I tip a flat rate and simply never return to the restaurant, etc if my experience was sub-par. Interestingly, tipping became popular in the US just after slave

I tip a flat rate and simply never return to the restaurant, etc if my experience was sub-par. Interestingly, tipping became popular in the US just after slavery was abolished, since many people resented paying blacks, full stop. Tips allowed customers to legally only pay the white workers. At least one deep-south state supreme court banned tip-based compensation, but the federal supreme court sadly overrode them. (This context helps me understand why some waiters in Europe get offended if you tip them.)