If I go to the bar for a drink, I'll leave something. If I make a mess that is cleaned up, I'll leave something. If I grab my own soda or beer and throw my stuff away, I don't leave anything.
But what do you do when people straight up DO NOT want you to tip? It offends them if you do, so....?
So, if you are at a bar, ask the bartender for a beer, he says that'll be X dollars, you don't tip? It's rare to get a receipt at an airport club unless you order premium liquor.
What about for a call in to go order? They give you a receipt for the food ordered but there was no service besides handing you a bag, do you tip that?