Wii U Gamepad and cost, along with the Wii U itself currently not being an attractive product for the mass market.
The Wii did so well with Wii Sports because the Wii Remote was revolutionary. It literally changed the way we play and made gaming accessible to people the industry simply never got to before. The Wii U Gamepad simply doesnt have this accessibility or mass market appeal.
Wii Fit again did so well because it was revolutionary at the time. There was nothing like it, it was the best you could get. It went hand in hand with the Wii philosophy of targeting the expanded market that wasnt available on competing platforms. To get the best, you had to get Wii and Wii Fit. As of right now, this isnt the case.
The Wii U Gamepad is Nintendo's biggest enemy in regards to the mass market and games like Wii Sports. Increased competition and a lack of faith in Wii U itself is the biggest enemy in regards to Wii Fit.
