How so? I mean, when you go to restaurant there is some sort of the contract, that for paying X you get Y food. Why would anyone not willing to do anything more beyond this deal should be considered an asshole?
People work hard outside restaurants also, often harder, and they don't get tipped anything.
People do want to work, for decent wages, not exploitation and begging via 'tips'.
I'm sympathetic to this, but surely the customers who don't tip aren't the ones screwing them. It's their employers screwing both them and the customers.
Federal law requires that the tipped employee be paid at least the regular federal minimum wage. I'm sure various state laws have something similar for when the state doesn't just match the federal minimum wage.
https://www.dol.gov/agencies/whd/fact-sheets/15-tipped-emplo...
There are, of course, plenty varying of ideas about the minimum wage.