I'm not sure what you're reading into what I said, but to reiterate: I've been seeing benefits personally from their work for years playing games that were not obtained via Steam. It's unclear to me why you think this is "exactly" the point you're making, because it's quite literally the opposite.
Because games are entertainment and this technology is not necessary for the betterment of humanity or enabling some kind of real technological progress, therefor it only really benefits who? Valve and really only in the short term. Once the contributions back are good enough, people will start to use the stack to cut Valve out. There for Valve only has incentive to contribute things that make their products great. If you enjoy playing older games on Linux because of Valve, that is only a side effect of the current efforts.
No, I still don't have any idea what you're trying to say honestly. At first I thought you were trying to say that they didn't contribute to open source in a way that actually helped anyone outside of themselves. I stated that it definitively helped me do something I already had tried to do sometimes but would sometimes have issues with, and no longer do in large part because of their work. As best as I can tell, you're essentially arguing now some combination of an assertion that it's impossible by definition for a company's open source contributions to benefit anyone else in the long run (which feels pretty reductive, like the economics arguments that everyone always acts purely rationally, despite the fact that plenty of people quite often don't do that) and that because it's only software that helps running video games, it can't possibly be beneficial to humanity in general (which independent of whether it's accurate feels kind of irrelevant given that the original proposition from the parent comment was that they did care about that and therefore wanted to support it financially).
