"You know those friends who are always late?" Noreen Butler says while waiting for her potential new friend to show up. "You end up letting them drop off."

Rebekah Kelley is more than 30 minutes late to join Butler for a Friday afternoon of swinging through trees and crashing into piles of mulch on a ropes course in Rockville, Maryland. It's an activity ripped from reality TV's playbook: Put two people in an adrenaline-pumping scenario and watch them bond quickly.

Instead of a "Bachelor" producer pulling the strings, Washington, D.C., matchmaker Michelle Jacoby arranged this meetup in hopes that Butler and Kelley will fall for one another as BFFs. After years of brokering romantic setups, Jacoby says she's responding to a need she sees among both singles and the coupled-up: Adults are lonely and hungry for more friends.

For years, Americans have been racking up thousands of "friends" on social media, but experts and those with waning social circles say it's particularly hard to cultivate deep platonic relationships. Love professionals like Jacoby and other businesses - from apps to co-living spaces - are trying to fill that gap by selling a stronger social life.

But will any of it help? Making friends as an adult is hard for the same reasons finding romance is difficult. There are fewer late-night hallway conversations or spontaneous weekend trips. People get busy with work, kids, caring for aging parents. Apps can help, but guess what - friends can ghost, too.

The explosion of friend-making businesses does help just by acknowledging that loneliness is common. According to a 2018 Kaiser Family Foundation survey, 2 in 10 Americans report they often or always feel lonely. Adults younger than 50 were more likely to feel that way than those 50 and older. Sixty percent of those lonely folks said there was a specific cause, and the most common answers they gave were death of a loved one, physical or health problems, being away from family, and divorce or separation.

There's some evidence that this has become more of an issue over time. In 1985, the average American had about three close confidants, according to the General Social Survey. In 2004, that number hovered just above two; a quarter of respondents reported having no close confidants. (The survey question hasn't been asked again since.)

The causes are hard to prove, but there are some hypotheses. Fifty-eight percent of Americans in the Kaiser study saw the increased use of technology as a major reason for feeling isolated (though other surveys are mixed on this issue). Remote work has been steadily rising. According to a 2016 Gallup survey, 43 percent of U.S. employees worked in a different location from their co-workers at least some of the time, up from 39 percent in 2012. Americans are staying single longer; the median age of first marriage is 30 for men and 28 for women, up from 23 and 20 in 1960.

Supposed solutions to loneliness are everywhere: When co-working spaces rent desks to digital nomads, they're also hawking a sense of belonging. Co-living spaces - rooms for rent plus communal living or dining areas - say they'll give you not just as a roof over your head but warmth in your heart. Some places, such as WeLive and Roam, combine co-working and co-living to offer 24/7 espresso shots of togetherness.

Exclusive social clubs popping up in cities try to re-create the feeling of community that Rotary clubs and bowling leagues used to foster, but with higher price tags, creating a phenomenon that Priya Parker, the author of "The Art of Gathering," calls a "venture capitalization of belonging." Therapists and friendship experts offer workshops on cultivating new connections. A video game for helping people make and maintain friendships is in development.

Dating apps Bumble, Chappy and the League have added friend modes. The friend app Meet My Dog is specifically for canine lovers. But most of the friend-making apps - such as Hey! VINA and Monarq - are targeted at women seeking girlfriends. Tourlina matches solo female travelers.

Peanut, which has more than 1 million users, connects moms. When founder Michelle Kennedy had her first child at 30, none of her girlfriends were moms yet. While on maternity leave from her job at Bumble, she was lonely - so she decided to do something about it. "I'm going to take everything I know about dating, and apply it to finding mom friends," Kennedy says.

Peanut matches can lead to in-person meetups - someone to join a mom and her child at Baby Gymboree, for example. There are also message boards where women can share advice and frustrations on sleep training, breast-feeding, going back to work and more. "Both are valid forms of friendship," Kennedy adds.

If those methods fail, you can use temporary ones like RentAFriend, which lets you hire someone to join you for a movie or a baseball game. Or use Chuck McCarthy's People Walker - he'll accompany you on a stroll around Los Angeles, and runs a network of hundreds of walkers who charge up to $21 for 30 minutes.

McCarthy walks with teleworkers who need to get out of the house, actors who need distractions, even people who just need someone to accompany them from their car late at night. On a recent walk with this reporter, he offered unsolicited advice on a movie script, pointed out the coyotes and castor bean plants along the trail and expounded on the merits of giving up dairy and gluten.

McCarthy feels such in-person connections are much better than the ones on Facebook. "It's like being cold and having a giant blanket on versus just being cold," McCarthy says of the false sense of warmth created by 3,000 social media friends. If you're still shivering under that blanket, "it's even more frustrating."

These friendship platforms are still in their early days - far more people are swiping for dates than swiping for pals. It took decades for online dating to shed its aura of desperation. It could be a while before perusing strangers' platonic profiles or hiring a hiking buddy feels natural.

Miriam Kirmayer, a therapist and friendship expert in Montreal, says some of her clients in their 20s have had luck on friend apps. But others bristle at the idea. "I'm trying to avoid saying the word 'pathetic,' " says Chris Allbritton, a 50-year-old man who's had trouble making new friends in Washington. Instead he calls it "odd and inorganic."

Megan Propps, a 46-year-old who's tried Bumble BFF in two places she's moved in recent years - Colorado Springs where she now lives, and Amelia Island, Florida - doesn't think these apps work for her demographic. While she messaged with a few matches, Propps didn't meet up with anyone. "There wasn't enough people using it to get a good range of people I shared interests with," she says.

The only person she really connected with in Florida came the old-fashioned route: She and a fellow beagle owner would walk their dogs together several times a week.

She's also found it useful to be open about her search. "One of the things that has helped me," she says, "is just to allow myself to be vulnerable enough to say: 'I'm looking to build friendships.' "

Just as the internet didn't automatically solve dating, Jacoby is betting that people will pay for a more personal touch. She paired Kelley and Butler without a fee; she now charges $720 and up for three platonic matches (much cheaper than her fee for romantic matches).

But cementing a lasting relationship isn't just about seeming compatible. It requires shared experiences and showing up for one another - again and again.

"Noreeeeen!" Kelley says as she arrives at the ropes course for her platonic setup. "I hope you don't break up with me because I'm late." Kelley brings a big smile and a small gift: a face serum and lip gloss from the skin care company she runs.

Kelley, 51, and Butler, 46, are both entrepreneurs, one of the reasons Jacoby paired them. They're both divorced and active. They even look alike - pretty, slim blondes. As soon as they're awkwardly stepping into their harnesses, they're looking out for each other: They caution each other when their shoes are untied and bring each other cups of water. They pump each other up, saying "You got this," "Good job" and "I think you're getting braver." They joke about the dirt that's settled into their pants.

An observer huffing her way up rope ladders behind these women could be fooled into thinking they're old friends ... until Butler asks Kelley where she's from and how long she was married. Oh, right: These two are still practically strangers.

Shasta Nelson, a friendship expert and author of "Frientimacy: How to Deepen Friendships for Lifelong Health and Happiness," points to a study finding that it takes 50 to 60 hours to convert someone from an acquaintance to a casual friend. Nelson's own research has found that work is the most common place for adults to meet new pals. However, work is also making it harder to find time to socialize. Nelson says the typical lonely person isn't someone physically isolated from others; it's the overworked professional who's constantly interacting with people.

"I talk to a lot of people in customer service or retail. At the end of the day, they're exhausted," Nelson says. "Most of the people who are lonely, they're not hermits up in the mountains. ... You can build this huge network and still be lonely."

Those who work alone can try to build community into their days through co-working spaces. At least that's what Gideon Culman, a 40-year-old executive coach in Washington, intended when he joined a WeWork in 2016. Though he's made some friends there, Culman noticed that during the wine-and-cheese nights or pancake parties, many workers grab food and retreat to their closet-size offices. There's also a lot of churn, he says - with workers staying for just a few months while their main office is being remodeled, for instance. "I'm certainly warier now," Culman says of creating friendships at WeWork. "They're going to be gone soon anyway."

However, some who have joined such spaces find that casual interaction energizing. Jessica Guzik was 31, living alone in a one-bedroom apartment in Washington and wanted more "lightweight" socializing. So she moved - spending half of 2016 at WeLive, WeWork's adult dorm in Crystal City, Virginia.

"I wouldn't have developed my business idea if not for putting myself in that environment," Guzik says of starting a dinner party service. In 2017, she moved to Berlin and joined a co-working space called Factory. "I was just so grateful to have a living human being across the table for me," Guzik says, adding that a single conversation at Factory might be "the only meaningful interaction" she had in an average day.

Sometimes you just need a guru to give you a push. Julieta Whiteside, a 43-year-old married mom in Angwin, California, realized several years ago that she didn't have any friends she could call at 2 a.m. if something wasn't going right. So she read Nelson's books and attended one of her friendship retreats, which sparked an idea. Whiteside started hosting events - book clubs, hikes, shopping trips and gatherings at the local gelato shop - about once or twice a month, using coffee shop fliers and the neighborhood social network Nextdoor to get the word out. She hosted all kinds of gatherings, so that she would touch different people's interests. "After five years, my circles are full," she says.

Whiteside often hears from women who feel frustrated that deep bonds aren't being forged quickly. It took almost a year for her to feel close to the people who were attending her events. Recently, when she fractured her foot and sprained her other ankle, they were the ones who swooped in with an apple pie and offers to help.

Kelley and Butler haven't quite reached that level. A full season has passed since they careened down buzzing zip lines. They've seen one another a handful of times on solid ground - going to a dance performance and to a white party. They frequently check in over text.

But they're not BFFs. Not yet, at least.

"Really staying connected ... has been hard for us," Kelley admits. Butler has two kids; Kelley is child-free. They're both busy with the start-ups they're launching.

In the meantime, Kelley is often lonely. Many of her longtime girlfriends are busy raising young children or caring for elderly parents.

But she tries to focus on the positive aspects of solitude. Her time is fully her own and she can do with it whatever she wants.

She recognizes that friends cycle in and out as our lives change.

"Sometimes we are alone," she says. "That's part of life."