Why not? Lots of reasons. For starters, Champions Online turned out to be very good, and I'm not in the habit of expecting good luck twice in a row. My last outing with a licensed superhero game left me pretty cold. I already knew the game broke from a lot of accepted superhero conventions, and it sure didn't seem like a game that would encourage the same sort of roleplaying atmosphere I love. Last but certainly not least, it's always dicey playing a game designed for both consoles and computers, since frequently one or the other gets the better interface.
Despite all of this, I am happy to say that these fears were unfounded. Or at least unfounded enough for it not to matter, which is close enough to the same thing. DC Universe Online is certainly not a successor to City of Heroes, but it's a lot better than I would have guessed, and it's certainly an interesting game thus far in its own right.