We have to remember that Nintendo made a lot of the decisions for the Wii U design probably back in 2010, when the iOS market was really just taking off and the iPad was just launching.
I don't think they anticipated getting left at the altar alone by the casual crowd, they designed the console thinking a good chunk of the casuals were loyal to them and would come back for more.
If Nintendo knew today that they'd be screwed over by that audience, they likely would've made different design choices with the Wii U.