German reader here. Because of minimum wage you'd only tip if service was good (or always tip if you have enough money, my parents generation are more frugal than I am). Delivery services often get around minimum wage because they use the "Uber" trick and technically the drivers are "self-employed", always tipping those folks.

Anyway: Are tips taxable in the US? Here in Germany tips are tax-free under certain conditions: If I give it directly to the barber, waiter, etc., it is a non-taxable event, while if the employer collects the tip and divides it up under all employees it is a taxable event.