i tip because i feel like it, if the service is good i don't care if a tip is expected or not. i have tipped for pickup before, yes, if the order was complicated or they made an exception or they were busy, i will let em keep the change or slide em an extra few bucks.

yesterday i was at the supermarket. now in colombia the checkers are generally borderline retarded, slow and a disaster. this woman, who was kinda easy on the eyes as well, was very organized. I had 25 of one item and she quickly counted them and passed one *exactly* 25 times through the scanner. The other stuff she would enter as multiples and count quickly. Normally they would pass each item one by one by one by one and in very slow fashion. In short, I was impressed at her level of organization and that she checked me out fast the way a first-world clerk would. So I tipped her 5000 pesos (right now about $2 or, for her, probably about 2 hours of pay). i doubt anyone had ever tipped her before.

even if i were to get carried away in the moment like you or your elderly friend, why would i be mad about it? we are talking about a small sum of money and now someone else has it, someone else who probably needs it more, too.