this question is just like asking why isnt Red Steel going to release on the 360. its mostlikely an exclusive
With that example I can't see why it
wouldn't be exclusive; the game mechanics are so different from the norm, I would bet it would take a pretty long while to rewrite the code for a standard controller.
I'd love to see some console exclusivity, it would give me a reason to prefer one console over another... as it is most of them just come off the same. With little differences, of course. But it's the special games for only one platform that really make a console stand out.