I just don't like him. He's a lame character in design. He's also a western third-party character, from Ubisoft nonetheless, and I don't think he's as relevant as some make him out to be - if anything I'd much rather have someone like Crash in before him.
Edit: and yeah, I did list a western third-party character as something I want, but that's because it's a character I like, obviously.
That's a pretty lame reason to not want someone in Smash.
Some days I just blow up.