Why does Steam/Valve care so much about Linux? I know as devs we all would prefer to use Linux/Unix. But developer experience isn’t a good business justification.
It's because Valve's entire business model is currently reliant on Microsoft not being emboldened to try and lock down software downloads to only occur through the Microsoft Store.
15 or so years ago, Microsoft started making moves in that direction and Valve immediately started trying to build and sell Linux based gaming machines in order to try and protect themselves somewhat from Microsoft. Those Linux gaming machines (Steam Machines 1.0) were a massive failure because they were expensive, and had very very limited game support.
Valve then spent around a decade improving Wine, building Proton, and designing the SteamDeck, which was a great success for them and is now making lots of people take Linux seriously for gaming. Now they're moving up the value chain and trying to make Linux the go-to place for PC gaming.
They've still got a big battle ahead of them, but already Linux users are around 4% of active Steam users, and the Linux experience is rapidly improving. Meanwhile, Microsoft seems to be bleeding goodwill, and is actively pissing off a huge amount of their Windows audience while simultaneously giving up on Xbox, so this is really perfect timing for Valve now.
They don't want Microsoft to be able to use its control of the OS to push them out. It's not the Valve needs to control the OS, it's that they don't want a company that views them as a competitor to have said control. Linux ensures that they have protection from that.
You can basically tailor the OS specifically for the device and remove unneeded bloat. Also the threat of Microsoft and Windows as mentioned by other users. The introduction of the Microsoft Store with Windows 8 basically kicked off this whole move for Valve. While it took over a decade of work, its paying great dividends now.
Even for personal use? If devs preferred Linux so much, I'd expect them to use it at least in their own time. But, what the stats say is that people use Win even more when it comes to personal devices, and Linux, not even a tenth of a percent. If anything, that looks like that dev don't prefer Linux. They use when the employer pushes it onto them, but not anywhere else.
