I remember when a 10% tip was the expected norm
A very good friend of my grandma's went cross country with her son and his family years ago. On one of their last stops before getting back home they had stopped for lunch and the son asked if he could buy some toy that was for sale at the place they stopped to eat. His mom says no, it's too expensive. The boy says he has his own money and proceeds to pull out a pocket for of dollars and change. They asked where he got it. After the first couple places they stopped to eat he noticed his dad was leaving money on the table. So he was taking that after everyone had gotten up. Pretty soon he noticed there were some other empty tables with money left on them too.
Finders keepers
They weren't sure exactly when he started lifting the tips but it was kind of amazing the waitresses never spotted him taking the money. After the fact they did realize he always seem to be the last one to the car. Talk about embarrassment but at least the odds of them ever seeing any of those waitresses were pretty long.