Public trading results in short-sighted planning because investors can always buy/sell stocks and move on to whatever is profitable moment to moment. Private companies plan longer term because the investors benefit from the company's long-term success. Their profits come from the company's profits, not the value of the stock.
Make no mistake, Valve is in it for the money. They're as greedy as anyone. But they operate under a corporate structure that values the long-term viability of its platform.
And they're still assholes. They are all about lootboxes, DLC, etc. And they take a massive cut of sales. Do Sony and Microsoft and Nintendo do the same? Yeah - but they also provide the hardware platforms. Does Best Buy and Gamestop charge similar fees? Yeah - but they have the overhead of the retail locations. Steam makes stupid money off a download platform and game launcher.
Gabe is a billionaire yacht collector, not your friend. His greed just takes a longer view than that of someone looking to sell their shares from minute to minute.