I think robotics research is probably a reason why they're discontinuing it. Why support something that only exists outside the walled garden? Maybe not the only reason, but a reason. The device probably isn't generating profits, and the value gain on top of that is missing because the gaming community has abandoned it.
This is pretty unfair. Microsoft released Kinect 2.0 for Windows[1], with a developer SDK, specifically for the community to hack on. It even supports Windows Embedded.
I can't in my wildest dreams imagine that they thought that product would be a money maker.
[1] https://www.microsoft.com/en-us/download/details.aspx?id=445...
Even though it seems like Sony's interest to foster a community of high-tech nerds interested in AI and parallel processing, and even though it seems like it's Microsoft's interest in fostering a community of robotics and computer vision nerds, it turns out the Giant Corporations need lock-down control on products and have no long-term vision for supporting ecosystems or communities.
I think they were worried about people buying them up and not purchasing games.
They used about 200ps3 to find some prime number (cryptography related)