I think the Windows Store is incredibly important. Worked as a technician for a while, and the amount of garbage people installed from random sites is mind-boggling. Or programs that hadn't been updated in five years. Non-tech people need a safe source for installing software (that also automatically updates it) and as long as the store wasn't providing a significant amount of useful software (all of which is Win32), it wasn't ever a viable solution. It might be soon.
The problem is that Win32 apps are inherently unsafe. If you want a safe source for installing software, you need a sandboxed app model, which on Windows means UWP or web apps. Unfortunately the Windows store eventually decided to compromise safety in the hopes of attracting more apps (the container format that Win32 apps in the store use isn't a real security sandbox).
Win32 apps have been supported in the Store for a couple years now. You'll find ("real") Office, Paint.NET, Inkscape, VLC, iTunes, iCloud, Photoshop, and more in the Microsoft Store today.
Also, nobody wants to give Microsoft a cut of the software price if they can help it.