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The difference is that Valve is privately owned. They don’t have to please a board of shareholders who want to see the platform milked for the slightest increase in profit margins.
This isn’t entirely accurate. If Valve were a public company, the enshittification factor would increase significantly. The reason they’re great now is because the current board is the original founders who are passionate about their business, and actually care.
Private or not, once Gabe and the other old farts die, Valve will enshittificate. That’s almost guaranteed.
For that you need passionate people who are wealthy and not primarily driven to acquire more wealth. That seems to be very rare in large scale businesses.