###Don't tell anyone...

I think I can only speak for myself, and "right" or "wrong" is not applicable here. Although I strongly believe in the reasons @Zanna posted and elaborated, and I'd love to think my single motivation would be to do a "good thing to the world", to me personally, that is a meta thought. I only feel that looking from a distance. An excellent one, but still. Don't get me wrong, I am happy to contribute, and if I feel an answer or solution helped someone, I am thrilled.

There are however many things in life I can do, of which I feel they are useful and helpful to people, but I don't do them. To spend many hours here helping people, we need more than to believe in something or an altruist's mind. 
Then what is my motivation, on a "primitive" level?


I need to be creative, and I love jumping into issues that seem unsolvable. They are the crossword puzzles I need to feed my mind with. Furthermore, I love coding, and I think I can say I actually learned it for the greater part here and on SO. No clue if it ever will be part of some kind of a "professional" life (in the sense of "paid" professional), but to me, that is irrelevant, I think I got the level. Furthermore, I got many, many other things from hanging around here and contribute. Things I value.

The thought that it helps people is the additional justification for spending so many hours here (or any other community that serves open source activities), and a sweet bonus.