I strongly favor the "warm glow" explanation, but I'd take it a step further.
For most people, the warm glow is only worth it if they get social credit.
Those yellow LiveStrong bracelets are a great example. They're about $1 or so, and purchasers wear them around all day advertising that they care about cancer. How many of those people would have donated an equivalent amount (just a buck) without the badge of caring they get to wear around?
I just happened to read a clever speech by Michael Crichton on this topic today. I think his main point echoes yours (or yours his).
http://www.crichton-official.com/speeches/speeches_quote07.html
"One sign that science is not all bogus is that it enables us to do things, like go the moon."
I was wondering if engineers were less biased than other scientific types? They deal with the practical and concrete all day long, and they see their ideas either succeed or fail before their eyes--such as landing on the moon or exploding on the launch pad. Unlike social or psychological researchers who have the option of clinging to their theories through thick and thin, engineers are trained to identify and abandon incorrect ideas as quickly as possibl...