Because when I tip I do it for exceptional service. Not so someone can make their minimum wage. When I pay the price of the meal, that should cover costs. It does in most other 1st world countries.
I don´t think it´s fair that the lazy shithead waiter automatically gets the xx% as the insanely good waiter who went above and beyond. Then I have to tip even more to the good waiter. And the lazy shithead can keep being a lazy shithead.
Pay a livable wage to all, and the great waiters will still get tips to supplement income. The lazy shithead won´t. Works perfectly well in other places.