Bad tippers drive me nuts. If you don’t want to pay for service, get it yourself. We went out to eat the other day and next to us was a table of older people who had the waitress coming over every few minutes about something. When they left, they left a pile of change on the table.
We always tip around 25% just to try to make up for the jerks who don’t.
That's commendable, but I question the judgement of anyone who confounds waiters in a restaurant with delivery people.
As for waiters in a restaurant, I always tip at least 15%. For truly bad service, I have been known to tip 2c (after the meal, of course.)