The other thing I believe is that a company should seriously value consistency in their implementation of these sorts of features, and Nintendo is definitely a company that values consistency.
They do things like re-rating VC games through the ESRB and fully testing every VC game to make sure it works, even if it's basically a ROM dump that would certainly work with no problems.
The only reason we got off-TV play for Wii games is because the pad is being treated as a TV, and no real testing on a per-game basis is required, no pad control compatibility list is required, etc.
I think it's acceptable for them to forego a feature that might be technically possible, if implementing it meant that a number of legacy games would give confusing messages about disconnecting a CC that isn't there (since you're using a pad) or pointing a remote at the screen (that isn't there since you're using a pad). If people have to re-sync controllers every time they boot up a game because the pad is default controller 1 but the menu needs a remote, that is unacceptable.
Consistency is key, even if that consistency is cumbersome. At least when the game mentions the Wii remote, you are sure to have one connected.