Actually, via one of those fancy universal controller cable things, you can actually use a GameCube controller on the Wii U.
That has been my main gripe about Nintendo: gimmicks. It's Nintendo saying "Hey! Look! We can do this!", and it's not what people necessarily want. This is the precise reason as to why Lucario and Pokémon Trainer are practically useless in Smash Bros. Brawl; Nintendo focused too much on getting a gimmick working, and paid no attention to whether the character was good or not. Lucario's output damage went up the more damage he received, but by that time, you'd've been KO'd anyway because of how slow he is.
Nintendo and their gimmicks are the sole reason the GameCube is (and probably always will be) my favourite gaming system; no frills and fancy shizz, just pure gaming experience with a normal controller (plus I'm a sucker for F-Zero GX, Super Smash Bros. Melee and Mario Kart: Double Dash!!).