I figured out why the 720 requires Kinect to work

[yo_john117]

kain_kusanagi said:

It makes sense to me even if I'm not a fan of motion controls. MS wants developers to utilize Kinect 2. The original Kinect didn't get full support from devs because devs knew only a small percent of Xbox 360s had them. But if ALL Nextbox consoles don't just come with it, but only work with one connected, then devs can count on it and integrate it into their games. That might mean voice control or motion or some hybrid with a controller.

The Wii U ships with the GamePad for the same reason. If it was an accessory sold seperatly most devs would ignore it and just makes games with standard controls.

This. 

This reason is much more logical. It appears they want to make everything standardized so all games can be fully optimized.