Hmmph. I go out with my female friends every couple months or so, and we generally tip around 20%. If you've ever waited tables, you don't stiff the waitress.
Worst tippers? In my limited experience, the friends of the boss. In high school, I worked in one restaurant where a LOT of the boss's friends came in. They got their discount by not tipping. I quit after six weeks.
There are exceptions to every rule. I never used the word "all"
If you've ever waited tables, you don't stiff the waitress.
That is one of the exceptions. Best tippers are often people who depend on tips for a living.