I think people are so hung up on using the word necessity when what they really mean is compelling use. Most controller functions are not a necessity considering they can map to kb and mouse.
Anyway, the truth is Nintendo has not designed those compelling uses for Wii U yet through software, but we have seen some glimpses.
The most ironic thing is that a lot of interesting changes I have seen have been in "hardcore" games yet they get very little importance in reviews and such - map function, UI configuration, inventory management. Most of this attributes to a faster, more seamless experience, which is what the two new systems will probably be touting as the next gen advantage - less loading, faster downloading, screen snapping. Interesting to see if that will compel consumers though.