So how would it get bumped to M? Add in unnecessary language and gore? Some of us adults have small children we don't want hearing/seeing those things, and adding them would make it harder to play while they are around. As the other guy said, it wouldn't matter. Tons of kids play call of duty. Most people allowing their kids to play violent video games don't pay attention to the rating, and since the adults buy the game for the kids anyway, it would make little difference.