Yeah, and if Microsoft suddenly decides they want to shut Steam out then there’s not much Steam can do other than take them to court. And even if Steam exited Windows there’s still lot of popular publishers putting out Windows only games like Valorant, Battlefield 6, Fortnite, Genshin Impact, and popular software like Adobe that would lead to losing a significant chunk of the userbase that would not move to Linux due to games and software they use not being on Windows.

Another launcher whether it is Microsoft or Epic or whatever would just fill the void for third party titles and probably be glad that the main competition is banished.

So this market share situation is not quite like Sony, Nintendo, iOS, or Google who not only run a locked down OS but also are the monopoly and sometimes only storefront.

Google recently shifted to wanting to gatekeep what can be installed and wanting verification from even devs that don’t want to release on the play store, which threatens viability of alternative app repositories like F-droid. Which is what could happen to Steam if Windows suddenly decided to change their minds about how open they’ve been in allowing program installations.

So Steam situation despite their popularity is still reliant on Microsoft not turning into a bad actor. They are more Netflix. The go to choice in their segment, but can be replaced.