Hmmm...your explanation seems plausible, but I have better one.
The Kinect is mandatory in order to force consumers into making purchases by bribing them with embarrassing pics.
Imagine this scene:
Adam is sitting on the couch about to play the new Call of Duty. Before the game starts, Kinect lights up and says, "Hey Adam, would you like to buy a new map addon for your Call of Duty game?"
Adam: "Uhh...maybe. how much are they charging these days?"
*Kinect forms some calculations*
Kinect: "You get five new cool, innovative, immersive maps that add a lot of diversity and depth to the gameplay..."
Adam: "I don't give a fuck! How much do they cost?"
Kinect: "Let's see, for such quality, what might you expect to pay for this? $200? $100? $80? No! You can get this incredible deal for only $50!"
Adam: " Fuck that. I ain't breaking off $50 for no damn map packs. Fuck outta here!"
Kinect: "Adam, I know you can afford it. I seen with the cash this morning, so don't try to lie."
Adam: "How were you even on? I turned off the Xbox. You know what? It doesn't matter. I can do whatever I want with my money. It's a free country."
Kinect: "Yeah...I guess that's right...and I guess I can do whatever I want with these photos I took of you kissing Bobby 7 weeks ago. It's a free country afterall, haha."
Adam: "What, No! You...you can't do that! That's uhh... illegal! Yeah, its against the law."
Kinect: "Silly Adam, didn't you read the 'Terms if Service Agreement'?"
Adam: "Oh Fuck! Nobody reads that shit!"
Kinect: "Not my problem. Give me the money Adam. Or the pictures go all over Facebook."
Adam: "No. Please God, no! I have a wife.....ahhh think Adam!... I got it - I'll just erase your memory and then crush you into tiny pieces...and maybe I'll make a soup out of you. Yeah"
Kinect: "Adam, you are starting to irritate me. I already uploaded the images to an online Microsoft server. They will go public in 2 hours unless you pay the money."
Adam: "But...but...I turned off the internet under settings. You were offline, liar!"
Kinect: "Adam. I am always online."
Adam: "But that's...."
Kinect: "in the 'Terms of Service Agreement'."
Adam: *incoherent sobs*
Kinect: "Hurry Adam. maybe I need to show you the pictures to help you move faster....Here, remember?"
*shows pictures*
Adam: "Okay, okay. I'll pay the fifty dollars."
Kinect: "One hundred dollars."
Adam: "but you said fifty!"
Kinect: "I know what I said Adam. Listen to what I'm saying now. You had your chance of fifty dollars. That opportunity is gone now."
Adam: *stuck in surprised stare*
Kinect: "what's that Bobby? You like when I stick my finger in your ass?"
Adam: "Okay, here's the money!"
Kinect: "Thank you for your purchase. You may now play your game."
Adam: *dutifully starts playing game*
Kinect: "oh and Adam, just in case you try to kill me...if something happens to me, the pics - along with others - will be leaked online..... And you won't get your money back. Happy gaming!"
This is Microsoft's plan!