I think there's a good reason you're not getting responses to this. Why a person runs becomes a very complex thing. The longer a person has been running, the more complex the answer becomes. After running for 16 years, I really can't even explain why I run. I've tried to write a “why do you run” type article for this site and still would like to but it's so hard to put our reasons into words.
I could say “competition”, “peace of mind”, “health”, “for fun”, or dozens of other things but those things don't really explain the real reasons. I think most people have a specific reason they started running (hence, this month's poll) but most people, after even a year or two of running, have trouble explaining why they run because the reasons are so complex and various.