It's rude to throw a party with no refreshments.
Bill is throwing a BYOB party at his house for some coworkers.
Bill wants to save money on party supplies.
Bill decides to cut costs by buying cheap solo cups and paper plates.
Bill decides to cut costs by not providing any drinks.
The guests don't mind the cheap cups and plates after they get a few drinks in them.
The guests are thirsty because there's not enough drinks to go around.