I think the fact that Valve is still a private corp is a big part of it, yes. It allows for continued ownership by people who have meaningful beliefs of what it means to do something the Right Way and who run the business accordingly. This isn't to say that private corps are always "good" like that - the temptation to go for easy pickings and enshittify is always there. But some owners at least won't do that for various reasons, while a public company seems to always end up chasing short-term profits above everything else.