Don’t assume that wait staff earns standard minimum wage. There is a seperate, much lower minimum wage for waiters/waitresses. I speak from experience. When I was a waiter, my wage was about $2/hr. Practically nothing. Wait staff are in practical purposes, freelance employees and rely on tips to survive.
In certain cities they do...it’s been so mandated.
So they can do without tips.
It is not so in my area so I still tip.