I pride myself on being a big tipper in restaurants with table service, but when the point-of-sale prompts me for a 25% tip on a counter-service transaction bef

I pride myself on being a big tipper in restaurants with table service, but when the point-of-sale prompts me for a 25% tip on a counter-service transaction before I have even been served I balk. Why should I pay so much extra for service when all they did was hand me my food/coffee/whatever? I recently got into a big argument with my wife over whether and how much we should have tipped a "valet" who didn't fetch the car and just handed me my keys.