Co.Design: Why Did Apple Just Pay $360 Million For Microsoft’s Sloppy Seconds?
Because Apple can probably do a much better job at implementing the technology than Microsoft has thus far:

There is another way to use Kinect, too: with your hands. Simply raise a hand up to the screen, hover over any tile, and push forward to select an app. Close your fist to grab the screen, and you can drag it to scroll much the same way you’d swipe across a touchscreen. In Internet Explorer, you can even “punch” the screen with your fist or pull it away to zoom. Unfortunately, it’s even more finicky than the voice commands: sometimes I couldn’t get it to recognize my hands, and often I selected something I didn’t mean to.
Call me crazy.