Parkour has a purity to it that is hard to find in most pursuits. The thrust towards utility and awareness of one's own environment distinguishes it from "stunt performance." Danger and physical challenge are only part of the picture. It really invites a more reflective mode of thought than other athletics.
If you're interested in parkour, check out BBC's Jump London and Jump Britain documentaries. They're fascinating, fun, and inspiring. You can find them on Google Video.