system
A chat on subreddit /r/NoStupidQuestions
human
My wife and I were in New York several years back and we had a few drinks at the hotel bar before heading up for the night.

We had maybe 3 drinks each, and my plan was to leave a tip as we left the bar(we were sat on stools actually at the bar, not a table). As I paid for the third round of drinks  the waiter dumped my change on the counter and said blunty "you know it's customary to tip in the States".

I was so surprised by his tone that we ended up leaving and taking our drinks upstairs but still leaving the tip id planned on leaving anyway. Hindsight says I probably should have taken it to prove a point or something but I genuinely was going to do it anyway at the end.
gpt
Not to excuse your waiter's behavior, but usually if you're paying per drink instead of opening a tab you tip every time you pay.