"or you would tip if you got good service."
Good being the operative word here...my custom is to tip at least 15% if the wait person is attentive, notices when my glasses are empty, has a nice disposition, and offers to correct any problems when possible.
If I get better service than that, I give a bigger tip. I have been out before and actually tipped the bartender or wait person more than my tab if they have done an exceptional job.
We reap what we sow.........