I went to a religious liberal arts College and all of my friends who waited as their College job (all of them good Christians) told me the worst shifts to have were Sundays and Wednesday nights because people who hit the restaurants after Church never tip or leave tracts as tips.
Even Christian waiters couldn’t stand them.
Sad but true.
Second place goes to the hispanics - percentage tipping is alien...a buck seems to do the trick for them.
I did a couple years in restaurants, and the church groups were always chintzy. Big groups where half the people got water or ice tea and everyone left little or nothing for tips.
Middle aged women are also very cheap on tips. I would be called racist to mention who the worst customers of all were.
All the same, even 20 years ago in the midwest, a server who only earned $8 and hour was a lousy server. Where I worked, $12-15 was probably average and the really good ones got upwards of $20/hr. Of course the most the IRS every knew about was probably $8/hr.