I think it's something to do with being a person to whom the phrase, "Yes, I can do that," comes easy.
Reticence is a common trait- many people don't like to push themselves forward in a social situation. Perhaps they don't enjoy responsibility.
Other people like a challenge, can turn their hands to anything, and like nothing better than having to master something new.
I moved to this town less than three years ago. I'm now involved in running four of the societies and associations in the town, and a rock band too.
I've always ended up running everything I've been associated with, at work on in my own time.
Whatever these people are, in a small way, I guess I'm one of them.
When people want something done, I say "Yes. I can do that". Sometimes I know I can, but sometimes, I just think it would be fun to find out how.
Cheers
Dave