Are Windows PC gaming and the XBOX line in such a decline that they could be described as desperate? I really doubt it, but I'm having trouble finding data to back up either argument.
They have completely different ToS.
They've rebranded the Xbox Store and Windows Store to both just be the Microsoft Store and content you purchase them (e.g. Movies, Music, TV) is shared between the two. Some Games are "Xbox Play Anywhere" which means you can play them on Windows 10 or Xbox (e.g. Forza Horizon 4) but others are exclusive to either platform (e.g. Flight Simulator). Some games can be purchased for either platform individually (e.g. Halo).
Then you have the weirdness that Microsoft Flight Simulator 2020 is published by Xbox Game Studios but only available on Windows 10.
Oddly enough, part of the unpopularity of the windows store comes from frequent reports of instability in the performance of the windows store software. You would think the world's biggest software company could figure out how to create a digital store that's as stable as their competition, but apparently they cannot.
Steam has longetivity. MS stores mean that you rent the product for maybe 5 years or bit more.
On Linux we just have the WorksOnMyMachine certification, which is accordingly crowdsourced.