I do wonder why it’s creeping upward though given it’s proportional and would increase as prices increase - perhaps it’s a symptom of employers paying even less after controlling for inflation etc. when comparing then vs now

The minimum wage (roughly what tipped workers earn) has been falling for decades, so I think at least some of the upward creep can be attributed to the knowledge that the workers are getting screwed, hard.

I assume it is at least partly a status symbol thing when going out as a group to eat, especially amongst young people.