Although, my pardons to servers, I always thought a tip was supposed to be a VOULUNTARY expression of grattitude for service well done, not a mandatory way to supplement someone's else's income.
It was supposed to be. But today's reality is, restaurants don't pay worth **** because they figure the staff will live off their tips - so they have no reason to increase the unliveable base wage.

When managers raise the wages - maybe then. But they won't, and are letting tippers pick up the slack.

JME