As you could see in the PC gamer article + comments I linked in my previous post, many PC gamers (and even most of the editors of PC gamer) straight up refuse to use the Windows Store
for many reasons(but that's off-topic here). Also on this forum, the "what game launchers are you using" topic showed that the majority of PC gamers here don't use it, despite the fact that many of them have no problem using other clients like GoG or Battle.net.
Of course it makes sense that Xbox owners are more likely to use it, because of play anywhere, Xbox features and the console-like experience.
Personally, I'm still waiting for Phil to fix it/opening it up before using it. It seems he's working on it, but we'll have to see what the result is. Plenty of other great games to play in the meanwhile and I can borrow a friends Xbox to play Forza Horizon. :)