Being rude to service staff. Immediate indicator on who they are as a person. There is zero reason to ever be mad at someone making near minimum wage whose job it is to grab you a drink or check you out or something. It also shows that they’ve themselves never worked service, which is a rite of passage
“Why should I tip?! I’m already paying for the service!”
Immediately leave without even telling them to take a cab.
Edit: 1, I am in the US, yes.
2: the wording sounded like it implied a behavior of a date while out dining. I was answering based on how I’d respond if a prospective mate treated underpaid US staff shitty.
If I am ordering and picking up at a counter fuck tipping. If I’m actually being waited on then I’ll always tip if the service wasn’t dogshit.