will someone explain something to me about House?

As in why, if they've swapped out teams and Cameron and Chase are now lucky if they have one line apiece per episode, are the actors playing them still listed so prominently in the credits? Contracts? Or are they really ever going to be a real part of the show again after more than a season of being replaced? Why has Chase suddenly become House's personal surgeon? And why oh why has Wilson's place been taken by a jerk private detective? (although the previews for next week were a bit more promising there)

Not that I don't think the writers have boxed themselves in to the point where it'll take a crane to suspend the disbelief it'll take to bring Wilson back...