People in service industries DO get audited if they get tips. The assumed % is 8%. Which is what the IRS will tax you on.
When I was a waiter I had to keep a log of my tips for this reason.
Scream and squeal about how cool you are when you don't tip, but unless the waiter/waitress REALLY fouls up your order, you should leave something.
And if the service IS that bad, talk to the manager and raise a stink. At least you should get your meal comped.
For the record: the worst tippers ARE gaggles of women. They always wanted separate checks (BIG PITA BTW), and then would either stiff, or leave a paltry tip.
Next worse: People coming in with gift certificates. Their meal is free, but they think that no tip is part of the deal.
Next worse: single businessmen. (If you're a waiter). Waitresses tend to get over-tipped by these guys. But they also have to put up with the come-ons and butt-slappings.
Finally: Most Un-PC: Asian, particularly Japanese customers. Tipping is not customary in Japan. So they either stiff, or are exceedingly generous and polite. Black customers almost always gave crappy tips. And they did this to waitstaff of EVERY color. Black waitresses did not relish waiting on black families for this reason.
Best tippers? Heavy smokers (when it was allowed) and heavy drinkers.
One of my best tips came from a bunch of construction guys sitting in the smoking section. They ran my butt off getting them refills on beer. Mind you, this was at 2pm. When they left I expected the big stiffo, because I'm a guy.
When I got to the table there was a huge pile of dollars and change resting on the table.