I don't know your financial situation and noone is forcing you to tip. But if you make, say, more than 3 times what the people servicing you make, and you choose not to tip, I think that's quite selfish.
I'm suggesting employers pay their employees. This isn't a radical concept and works just fine everywhere else. They already do this everywhere other than restaurants. If they aren't paying employees enough, that's a problem. You don't solve that problem by adding an optional tax on customers that is kinda-sorta-not totally required. All that does is ensure that in a certain percentage of cases employees get paid zero percent of the invisible tax. I'm just saying make the tax visible and required and stop this weird dance we do in america.
Tipping should be illegal. Tipping is necessary currently most places. Both can be true.
In actual fact I wish we could stop dancing around the fluffy idea of when to tip and when not to tip and just expect restaurant owners to pay their staff and include that in the price charged for the goods. It's super annoying having to think about this stuff all the time.