EVERYTHING that Fletch said.
Plus, I see it as a sort of moving meditation in that, I'm not "thinking" a great deal when I'm rolling. I guess I love that no-mind state (which is easy enough for me - some would say
That flow-state appeals to me a great deal. That and the fact that I can train often without getting NEARLY as banged up as I get when I do hard stand-up. Perhaps I just don't want to have to deal with pain as much as I might have before (while still training in a HIGHLY functional art).
And because it keeps me active. At 41 (in a couple of weeks) that's pretty important.
So many reasons...