I think Nintendo learned from the Gamecube and the Wii that it's not profitable for them directly compete against Sony and M$ for the same market, so they knew they needed something fresh, something..."in." From there, it's only natural that they would try to expand on the "family funtime" concept of the Wii, while trying to recapture some of the "core" market they lost with the Wii. The U-pad is clearly their attempt at doing exactly that. It embodies and expands on the local multiplayer aspect of the Wii with it's (unprecedented?) ability to deliver 5-person multiplayer on a single console, and it adds another layer for hardcore titles with the expanded controls made available by the touchscreen. Well, it should, anyway.
So, in short, no, I don't agree with you. I'm sure that Nintendo, videogame developers that they are, went through several design choices and landed on the one that they found would make a substantial addition to their titles, and, of course, the one they thought would net them the most money.
