Voted for Want to Just Haven't Got to it Yet? (Whats keeping you from doing so?).
Time, mostly. While I am passingly interested it's not massively high on my list of things to do.
From a distance as CCG's go it doesn't strike me as having sophisticated or satisfying mechanics. I look forward to being proven wrong.
I was given a card the other day and that at least got me to login. I like the site and the concept generally.
Give it a try and you would be surprised. Its a game of skill you have to use the right monsters together to unlock each others special powers. You keep your melee attackers in the front ranged in the back etc. Theres more to it than it looks. Im a complete newbie when it comes to CGG's but the how to play tab breaks it all down pretty good and just by playing you learn new strategies. You should definitely take a look at the How To Play tab it explains the different aspects of the game.
Thanks for taking the poll appreciate your feedback.