In my observation, the non-tippers are usually a very small percentage, and are senior CA's... at regionals and majors.

I don't make a trip the bank to get ones, if I don't have any ones they may not get tipped if they can't break a larger bill (they might get a fiver as a tip in that case if they were on time and helpful).

They also don't get a tip if they don't touch my bags.