In reality, it’s likely a self-preservation move. Microsoft made what appeared to be a monopolistic move to control the entire Windows ecosystem when they added their own app store and the locked down S edition of Windows. If Valve both hadn’t invested in Linux and Microsoft hadn’t halted going down that path, they would have been screwed.
Being cautious of a corporation is never a bad thing, but remember: Valve isn’t a public company. They don’t have the same incentives and fiduciary duties that led to the enshittification of most other companies and services.
Ultimately, yes, everything they do is entirely for their own benefit. But, they’re also free to focus on their long-term growth and returns. As long as the leadership doesn’t get changed to a bunch of shit-for-brains golden parachute MBAs, they’re going to want to keep their customers happy. It’s good for them, and it’s not terrible for us. Everybody wins.
I would prefer they were a nonprofit, but I’m not going to complain when the mainstream alternatives to Steam are mostly comprised of shitty sales-focused storefronts created by companies beholden to their investors.