Why doesn't the Wii support at least 720p?

I don't get why Nintendo didn't at least support 720p with their console. I can't stand 480p, it looks terrible. It's better than 480i I guess but it just doesn't make sense to me. The orig XBOX went up to 720p and the Wii is more pwoerful than the XBOX in everything except teh processor which is only like 10mhz slower and the graphics cards which are equal. If the XBOX could do it why can't the Wii? Couldn't they release a firmware update to support at least 720p? They could just upscale previous games like SSB Brawl so it supports it and then people would be way more happy with the graphics... Someone tell me why Nintendo hasn't done this and if they plan to do so please...