Important to add: in fields where tipping is standard (notably, restaurant waitstaff), in many areas of the US the minimum wage is much much lower. Nationally, $2.13/hour. That pays their taxes... For all intents and purposes, restaurant and bar staff are gig workers that are working for a variable rate determined entirely at the customers' discretion. If you don't tip them, they're essentially working for free, or rather, the rest of us are subsidising your service.

It is a mind-blowingly terrible system, but until we fix it, "tips" (in the US, in industries that are traditionally tipped) are not a bonus, they're part of the base wage, and if you don't pay them you are absolutely freeloading.