This country is wide and disparate. 15$ in NYC is not equivalent to 15$ in the middle of nowhere Utah.
This is why states can choose to make minimum wage whatever they want. Simply blanket stating that 15$/hr for everyone is silly. But lets realize that many states DO require around 15$/hr (or close enough where a 1 dollar tip per table would net them 15 really easily)... and those states actually hold a significant portion of the population of the USA... meaning that most of the people you're talking to here on Lemmy are LIKELY from those states. Does someone who lives in a house in the middle of nowhere Utah have the same requirements for income? You can look on zillow right now... There's houses that appear fully functional for sale at $30,000 (357 results for less than 50k). Does that person need 15$/hr? Just because you're used to prices where you live, and demand those wages at your location, doesn't mean that those numbers make sense at other place in the USA.
So the real question... Where you live... on the table... are they already close to 15$, or close enough that a 5-10% tip which is what used to be customary would still get them over your magical 15$/hr number?