The answer to the OP's question is:
Because a bunch of whiny tourney nerds who think THEY are the only fans that matter when it comes to Smash, complained to the heavens that this new SB was going to be HORRIBLE, because they couldn't cling to their beloved GC controllers, because don't you know, Melee is the best game ever created.
And as we all know, the squeaky wheel does sometimes get the grease. SO much so that Sakurai is even bending over backwards to put a Tourney-Tard mode in the new game, with No Items + Final Destination being the rule. I'm surprised the mode didn't also include Fox Only.
Jesus fucking Christ. So much ignorance squeezed into one post.
But out of curiosity, why do you seem to care this much about a non-issue? All Wii and Wii U branded controllers will be supported and no one will force you to use the Gamecube controller.
Also, tourney "tards" never asked for Final Destination-only. That part just shows how limited Sakurai's and the Namco team's knowledge is about the competitive Smash community.