Like I've said, I'd like to hear anyone's reasoning why not. And no, 'Just because Nintendo' doesn't count. All I've read when mentioning this is comments such as yours or the other one I quoted without giving any reasoning behind it. Why not..?
Like I've already stated the PS2 was the lead platform for the vast majority of 6th gen multiplatform titles, supplying up-ports to the PC, Xbox and Gamecube. The Wii U being the platform with the largest marketshare, being the least powerful of the three and having a similar architecture to the other two systems makes it an ideal candidate for supplying up-ports to the PS4 and 720. A developer won't want to develop a game on the PS4 or 720 as the lead platform and find that the Wii U isn't powerful enough to down-port the game to.
Publishers with any sense (an oxymoron I know lol) will always want a U SKU for their current gen titles due to cheaper development costs. Ubisoft said that it cost them 5m Euros to port games from the PS3/360 to the U (might have been Assassin's Creed III but I will stand to be corrected) and developers save the cost of forking out on an extra licence for Autodesk middleware, Havok middleware, Greenhill's MULTI IDE and the Unity 4 engine due to getting a licence for each for free with every devkit.
I think my reasoning is pretty sound but I'm willing to listen to alternative reasoning from others, and so far I've read none at all when mentioning this.