Here's an experiment. (I've been reading Ariely). I bet that the amount of a tablemate's tip is a bigger influencer on tip size than the quality of service. Or back to the Tarantino movie, if there were more people in agreement with Mr. Pink it wouldn't matter how good the waitress was, she'd get a smaller or no tip.
I'm meticulous about my tipping and always tip everybody. It's a habit I picked up as a traveling consultant road warrior on expense accounts. I tip 20% rounded down to the nearest buck. I never write that amount, I just put in the bottom line and let them figure it out. If you want the money, do the math, I say.
I do distinguish.. now that I'm signaling I may as well got the whole nine..between waitstaff, cabbies, bellmen and janitors. My wife always tips the lady who cleans the hotel room. I don't know where that came from and I never do it. I never tip for takeout food. I tip cabbies but don't mind if I don't. The person I would never stiff is a bellhop or a shoeshine boy, no matter what.
Hmm. Now whom do I cheat on a regular basis?