I think its more MSs heavy-handed attempt at controlling the PC gaming market. Right now its open and free, anyone can release a game for windows and dont have to pay MS anything. But now they can say "Hey, use our little toolkit. Get VOIP in your game, get exposure, people love achievements, easy console port for more money, etc" and they hope devs sign up. Then they can get a cut of game sales (esp on that 360 port), and they get PC gamers to cough up for Live service.
Mo' money, mo' money, mo' money!