What's important right now is converting people away from windows. I expect Steam OS 3 to be much more beginner friendly than any other distro. If an average PC gamers first impression of linux is constant troubleshooting, they're not going to try another kernel; they're just going to go back to windows.
Even if valve stops support later, they will have still introduced many people to linux in a beginner friendly way and wrestled the gaming ecosystem out of microsoft's grip that much more.
And from ex-ubisoft devs no less; the undisputed king of mediocrity. It's a testament to how utterly crushing the weight of shareholder influence and middle management bloat is on the people working there. Creativity cannot flourish within a publicly owned company that only seeks profit and nothing more.