ehh. i always tip it seems more polite and anyways, it helps a lot on the waiter's pay. but. if they did something that pissed me off, i wouldnt tip
^ yeah it's easy to say if ya'll dressed up with friends out for dinner on a friday night at a busy restaurant and the waiter/tress come chasing you at the door asking for tips and all eyes turn to ya'll .. ahhhh .. saving face is important ...i guess it's okay for gal to do since they're bitchy but guys, it's embarrassing.
I agree with you to a certain extend. Some professions such as bartenders and waiters depend on your tip as part of their salary. They dont make minimum wage so they need your tip to supplement their income in order to live. But you are right the cashier pouring your coffee does not have to be tipped because she makes at least minimum wage but it would be a nice jesture.