Valve has been using MoltenVK to run Dota2 on Mac1. I'm a bit worried that if Valve would cut the funding on MoltenVK2. Furthermore, CS:GO had been an example of a cross-platform example for multiple-player game. Valve's games may still support Linux/SteamOS, but what if other developers only release their games as win-only in future?
I agree. It's a mistake for Valve to reduce platform support as it becomes a justification for dropping other platforms for other developers as well.
I know that MacOS is a bit of a pain to support right now with how steam and third party applications are treated, but it would be a bigger issue for Apple to drop support if Valve maintained a strong presence on the platform via steam. With the way things are now, Apple might rip the bandaid off and just remove the ability to have third party stores on their computers. This is already what they do with Iphones/Ipads
One dev does it in his spare time. I use it to run games that aren't on Steam like Ubisoft and Blizzard stuff.
But yes, as a software company you'd probably have to pay someone to create and maintain a similar release for your own use - but that's part of being a software company.