My guess is that the Wii is just not the console that devs want to develop for. They want either high power to make things that were impossible last gen, or online abilities. With the Wii you have nothing of that, and even worst, with the super simplistic controllers you have to simplify games to death. That said, it's those specificities that made this console so popular in the first place, the shitty hardware allowed some super aggressive price tags, and the simplified controls managed to grab a new audience. I can understand Nintendo doing things its own way, after all, the Gamecube was perfectly capable of handling PS2-Xbox games, but it still failed