I think most of the problems here is that Microsoft has it's fancy new UWP executable which they're pushing like crazy, while Apple still hasn't found any major

I think most of the problems here is that Microsoft has it's fancy new UWP executable which they're pushing like crazy, while Apple still hasn't found any major issues with .app which would mandate the sort of architectural rebuild requires to add these features in. As far as I can tell the Mac App Store just ships .app bundles which meet a certain set of requirements(instead of the user downloading a .dmg containing the app).