Why Peach isn't in New Super Mario Bros Wii

So Miyamoto claims that they didn't include Peach as a playable character because of programming issues surrounding her skirt.

http://kotaku.com/5384278/miyamoto-asked-why-peach-isnt-playable-looks-to-skirt-issue

I'd've figured it had something to do with that gameplay mechanic involving picking other players up by their legs and walking around with them.

Peach and Mario (c) Nintendo