I wonder what the overall adoption rates are for UWP. As someone who's written Windows software since the 90s, I can't shake the feeling that Microsoft just churns out completely new development stacks every few years.
On one side it is a big reason why they have achieved their market size on the desktop, on the other side we reach this kind of situations where new tech improved tech like Singularity, Midori, Longhorn or now UWP gets thrown into the garbage can in the name of backwards compatibility. Quite sad.