Think about it, more than half of that 38 aren't even close to being viable, and of the characters that ARE viable, more players are switching to MK from them. How many good Pikas and Kirbys are there? Then tell me how many good MKs there are.
HeroMystic said awhile ago that Play To Win mentalities were killing Brawl, and I think he's absolutely right...I've believed it for awhile now. If you play to win, there's no reason to use any character other than the best (MK). However, if everyone (or at least the majority of top players) are using MK and actually winning tourneys, we get bombarded with charts and graphs saying "this needs to stop! He's winning too much!".
If you Play to Win, there's no reason not to go around the rules and plank or grab the ledge 49 times or fly underneath the stage or play extremely campy. You do this, but then people complain when it happens...I think that's all that this "Ban MK" business is about.
Brawl becomes a broken game when you play to win.