MS doesnt own them, they merely have reached a contract with them that the Xbox is the soul CONSOLE to develop on....Handhelds are another story. And like you said, they need to make more money. MS is making them cash with consoles, but why not make a bit extra on handhelds? After all, in MS's eyes, a dominant DS doesnt really hurt things.
Heck, MS has actually tried to reach agreements to bring Rare games to the DS like Viva Pinata.
Back from the dead, I'm afraid.









