i'm in your conscience
SSB doesn't need to be M. Do we really wanna see blood splattering everywhere? I think since it's a plethora of familiar Nintendo characters, that's why it's not M. And you'd miss out on some of the market. I think parents disregard the T ratings for Melee and Brawl since they know it's Nintendo (if I were a parent, I would. I don't think it's that bad of a game so sure, 7 year old Syd Jr can play it if he wants to) and if you slapped M on it, I think parents would be more wary. Then again, you have parents buying Call of Duty for their 6 and 7 year olds without paying attention to the rating at all so why do we even have a rating system anymore...lol.
But it would just seem strange for Nintendo to make their fighting game rated M. I mean...it's Nintendo.