Ken: My springing to Thom's defense was maybe as knee-jerk as your reaction. But as I thought about it later, experiences of mine came to mind:
I do a LOT of road trips. Iv'e been in all 50 states 6+ times and 92% of the counties in the US, including all within 1300 miles of the Atlantic or Pacific. And I stop a lot to help people stuck along the road.
Sometimes, I've stopped when 10,000 people and 5 highway patrol have driven by. And I'm pretty mechanically, handy, and can usually get someone on their way. I've noted that:
Rich people don't offer to pay. A motor-home driver thanks me, but never offers me money or anything else
Really rich people - Jeez! I changed a tire on a Rolls Royce once on I-87(?) just south of Springfield, MA before the CT border. And he never even said "Thank you". Just said "Bye" and drove away.
Poor people ALWAYS offer me something for my trouble. They want to pay me if they have any money. I've had a guy who really want to give me his fishing pole in return for the 2 gallons of gas I put in his car. He didn't run out of gas because he was stupid, but because he had no money. I don't want his stuff, just to help out. But, in retrospect, my old line of, "No, I don't want you to pay me, just help someone else someday." didn't work as well for me.
I'm come to think that different people want/need to respond differently to my generosity. I can retime their ignition, jump their battery, add two quarts of oil, drive them to a gas station, etc. They may not have the skills, resources, or ability to help someone else out like that. And maybe it's just outside their comfort zone. I think they want to feel complete about their "transaction" with me. I'm gifting. I want them to gift. But they're in my debt and they'd rather not be. So, increasingly, I let them "settle the books" in whatever way they'd like to. I encourage them to help others, but I realize that my donating thousands of dollars and hundreds of hours every year, is, in a lot of ways, a luxury item that most people can't afford.