The more you question this norm, the higher the likelihood for change to more healthy business practice.
I am sure they would be all for a $15/hour minimum wage, as long as tips were still on the table. However, $15/hour and “we don’t accept tips” sign…you would get a big nope. I doubt you could convince them that it would be better for them to earn $300 for their 20 hours of work.
In Europe we are still tipping, but the waiters do not depend on it. This is a much sweeter situation if you ask me, voluntary good service, vs. forced good service, when you have to worry about rent for the next month.
The question of should their employer pay them more per hour? Well, I think the market does a pretty good job of managing that, especially now that in many places in the country restaurants are having a hard time finding the help they need. If I need a server, and my offer is I’ll guarantee them at least $10/hour…that is going to attract workers to me over the restaurant next door offering only $7.5/ hour. If I am fully staffed with good servers, I can attract the customers who will pay my tip earners for me compared to the place next door with lousy service.