Legacy reasons. Microsoft is pushing for more adoption of their Universal Windows Platform, but just like Apple they’re having a hard time getting people on board with their restrictions. And, you know, nobody wants to re-write their apps when everything works fine the way it is.

UWP apps are all stored in c:\program files\windowsapps, a hidden directory owned by the system so your user account can’t see it or its contents without some overrides. It’s like the Applications directory on MacOS.