The definition of service is not "someone does their job". We should also recognize that food service workers are not, in fact, selfless and saintly as a collective group and have skin in this game.
I agree, the tipping economy in the US is corrupt and rigged to benefit the owners. Service employees should be paid a living wage. However, currently they're not, so while I would love to only patronize establishments that pay a living wage, that's not really an option. In the meantime, I don't take out my frustrations on the staff who are the victims of this system by short-changing them.