I can honestly say that I have seen more selfless acts on this single website than I ever did in the JW congregation. Why is that?
I'm no expert on the human psyche, but here's my take. Many JWs (but not all) are mainly drawn to the cult because the "end is nigh" and it offers them a fantastic reward. They're serving Big J of the WT cause he'll pay out large. "Because its just the right thing to do" is tagged onto that. So maybe thats why you apparently see more selfishness among dubs.
The really caring people among the dubs, who finally catch on, "get out of her" and that explains the awesome displays on this board. All of the posters here have made my icy cold veins warm up with their genuine love.
In defense of many dubs I've known though, they've done some pretty selfless things. Most people, dubs and non-dubs, are a balance between selfish and altruistic with each of us at different points along that dichotomy. As social animals we're cooperative. If you're a cynic you can still argue its all strictly done out of self interest, but I'd like to think that we're ascending to genuinely more selfless creatures.