I dunno about the Mac but the Windows Store is a ghetto in Windows. Real applications are distributed with ordinary installers, you only go to the Windows Store because you need some crapplet to work the scanner on your printer or something.
Oddly, you can download games with Steam and it “just works” but I’ve had the database for the windows store get corrupted numerous times and been told by support and MS devs that I should nuke my account and reconfigure all the applications I use every day just so I can attempt to run one crapplet. It is silly because I know there is a utility to rebuild that database that runs when you do a feature update.
Do you think any developers would be using the app store on mobile (and giving up 1/3 of their money) if they had a choice?