Just wait 5-10 years and it will probably be the same way on Windows and MacOS. They will argue that installing arbitrary, unvetted software through the web is dangerous, so it's only reasonable for Microsoft and Apple to make this very difficult and instead promote installing all software through their app stores (which they already start doing). Once software is primarily distributed via these stores they will also…
If there was one thing that would push desktop linux into everyone's desktop in enterprise environments, it would be a move like this. And once that happens, similar to the initial home computing revolution, workers would bring it into their homes too.
As another comment mentioned, they'd almost certainly lose the desktop market among PC gamers when Valve & others refused to go along, and Valve's linux distro would be a very popular alternative.