The problem lots of people fail to think about is the issue about having two xbox's in the same house. Maybe one for each brother, one for you one for you kids, etc etc... Most of this will be tied to ONE account or ONE system so multiple system owners are screwed. Same thing if you decide to bring a game over to your friends house to play or if you wanted to give a game you finished to a family member or friend. Nope nope and nope.
"You shouldn't be asking HOW things are, given that we already know there is something..but rather WHY things are, as opposed to there being nothing."