They’re a capitalist company trying to make as much money as they can.
Unlike publicly traded companies, Valve is not beholden to shareholders, so they, unlike most others, are in a unique position to not JUST maximize profits. I think it's okay to point at Valve as an example for other companies to be more like, because most are still worse. But obviously we can always strive for better, as well.
(Also, out of curiosity: Under a capitalist system, can you have anything BUT a capitalist company?)