Shiggy gives a different reason for no online in NSMBWii

[Gamerace]

If Wii had a camera, or at the very least a practical voice interface for online, it'd make a lot more sense to have online multiplayer. WiiSpeak is lousy. My friends make me turn it off because they find it too distracting when we play online. We end up using phone instead.

NSMBW online with no way to communicate with your friends would not be very fun at all. It'd be little different to playing with an AI partner.