That's what nintendo said about it:
“With Wii, when we brought out motion controls and introduced that as a new idea in gaming, initially there were people who didn’t understand it. Three years later, our competitors both came out with their own motion control systems.”
“We announced second screen gaming last year, and it’s somewhat flattering that it only took people a year this time around.”
“Smart Glass just doesn’t look like a peripheral for a games system. Microsoft may have used TV shows and IMDB to showcase Smart Glass, but as far as games go, gamers trying to incorporate Smart Glass into play sessions may find themselves limited by their number of hands.”
“I’m not sure how, as a gamer, I would manipulate a second screen with most hands on my controller. We don’t have three hands, unfortunately.”