I play it here for the convenience. My time gets broken up a lot and I'm on the go often so it's a great way to get games in.
Who plays only online chess (CC) ?

I pretty much only play cc chess here. I'll play the occasional live game but I prefer otb, I don't know why, it just seems more satisfying to me.

Over the board, specifically tournaments, is the best chess experience by far to me. Sadly I can't run around doing that all the time!

I only play "online" chess on here. Never OTB as many of my chess friends died in the last year. I also never play "live" internet chess.
I limit myself to 2 "online" games on here; one of which must be the fourteen days per move variety.

I never play live chess here. I don't have enough time to think in a short game, and I rarely have a big enough block of time to commit to a long game all in one chunk. I also prefer having an effectively infinite amount of time to think. The clock may be ticking on each move, but you can keep resetting that clock until the game plays out. I like that. It also fits well with my lifestyle, where I work long hours at a weird time of day, and have very little free time each day.

I also only play correspondence-style, and I like to play it with time controls as long as possible so the clock is simply not an issue. In ± 7 years here, on and off, I've just topped 200 games, and apart from the occasional opponent timeout, they've been relaxed, friendly affairs where the result hasn't really mattered.
From what I've read here of live chess, there seems to be problems with lag/disconnecting etc. Not interested. Just like to play the odd game without hassle - it's supposed to be enjoyable.
Finally, I have a family, I work, and only a certain level of interest in chess in any form. As it comes so far down the priority list it has to fit in with everything else, and correspondence chess does that very neatly.
I play an occasional live game but very occasionally - usually if I need to wind down just before going to bed. Mostly I play long time limit games (three days or 1 day). It suits me very well. I like to look at a position, try a couple of lines and then come back later when I often enough find that my thinking has matured and I either know that my candidate move is good or that I have to look much harder.
I agree with an earlier poster that manners are good and people are obviously enjoying their game. I read with amazement in the forums about the unpleasant behaviour which goes on in the fast time limit parts of the site. Youngsters (or the very immature) I think.
Anyway I am happy that chess.cm affords me the chance to meet so many congenial opponents and the chance to play at the times that suit me. The additional chess resources on the site are a considerable bonus vote chess in particular.
Who of you guys plays only cc Chess here and why?
I personally feel real beauty can be archived through cc Chess, even if it's online.