But there is SatoshiDICE, which is designed along similar principles and seems to get some use.

I guess part of the problem is that people who play roulette are not very sophisticated about it, since it's an expected loss anyway. I could imagine poker players being interested, but this protocol doesn't really fit: it reveals what the deck was at the end of the round (players who folded do not want other players to know what their hand was). I think that the attack that online poker places worry the most about is colluding players, and P2P cryptography doesn't help there.