Because I write good stuff, and because you read it.
Occasionally there is interesting stuff here -- I've enjoyed, for instance, David Mizner, gjohnsit, Bobswern, Colorado is the Shiznit, Ray Pensador, One Pissed Off Liberal, FishOutofWater, TheMomCat, CIndyCasella, Jesselyn Radack, and numerous others. It's a good place for culture.
As you may have guessed already, I don't take the site mission terribly seriously. Why should I? The people around here who do take it seriously are showing all sorts of ulterior motives in doing so, and they aren't interesting motives either. I've pointed the way forward, but, hey, if STFU diaries and "the Republicans are bad" diaries are really your thing, don't let me stop you.
My perspective is shared by few Democrats, if any at all -- but so far I haven't been kicked off the site. Part of my survival strategy is in being generally positive and proactive.
You know what I'd really like to see? Let's get the Occupy people together with the climate change activists. Throw a nice party, with good food and everything. Maybe it can start here, and maybe it has to start elsewhere. Everyone has to have a location.