i will always tip excessively, no matter the service. i've never had service so bad where i didn't want to tip at all. as a waitress, if i'm given a 20$ tip, i'm expected to give 2$ (10%) to the kitchen, 2$(10%) to my runners and 2$(10%) to my bussers. that 20$ tip is suddenly 14$. and that's not even counting at the end of the night, when i have to tip out the bar, which is usually tabulated as 25% of total alcohol sales. waiting tables is a pretty incestuous biz, most everyone has worked everywhere with everyone else. i don't know another waiter who doesn't know another waiter. if you are consistently a shitty tipper, you can bet your ass that everyone will know about it soon enough. there is also a hierarchy. i always shoved my tables full of australians off on the new girl because i knew they wouldn't tip and i didn't want to be bothered wasting my time for nothing. my time is already only worth 2.15$ to begin with, no reason to spend a full hour waiting on someone when you know you'll come out negative (after paying out your bussers and runners). there would be couple of guys who would always come in, be rollin real hard and shit, run up a 500$ and leave 10$ as a tip. you can bet your ass that after a couple weekends no one would take their table. management would always listen to complaints of high bills and negligent tips and didn't penalize a waiter who skipped over a high bill/bad tipper. at some point it becomes incredibly offensive. if you wanna work up a 500$ bill and then not tip, you don't deserve my service, shitty or not.
a lot of this is also fought by auto gratuity, which is helpful, but doesn't cover everything all the time.
servers are expected to take a load of shit for the place -- be the face to complain to, even when it isn't your fault, pay for their own uniforms most of the time (which technically is illegal, but who stands up for waitresses?), and pay out of their own pocket for every skipped tab (which is incredibly fucked up, but who stands up for waitresses?), and have no sort of protection either in organization or by the people they work for. ON TOP OF THAT we're expected to declare our tips to the IRS when most service industry people can't prove their income to get any sort of assistance from the government or a school loan or a down payment on an apartment or anything like that.
someone who is a shitty tipper is a deal breaker for me in any sort of relationship -- friend, lover, whatever. it's like if you can't be compassionate to someone who you KNOW is working in a situation that's stacked to work against them, i don't want to be your friend, or even around you, in any way.