There are two requirements to be considered a monopoly, or fall under antitrust laws:
Have a large market share
Be able to force competing products out of the market
Steam meets point 1, it doesn’t meet point 2. On the other hand, things like the Apple App Store, don’t meet point 1, but meet point 2, which makes them more likely to fall under antitrust. Windows meets both points, which is why the US sued Microsoft for not letting people choose their browser.
Being popular does not make steam a monopoly… My son plays 80% steam games but has Epic launcher installed and plays rocket League regularly
There is nothing in Steam preventing or even making it hard for you to run PC games in any other way
having a market share like that is a form of monopoly. It’s obviously different from absolute monopoly, but they wield too much power as is.
And to be fair, running games on linux without steam is definitely more tricky than without.
There are two requirements to be considered a monopoly, or fall under antitrust laws:
Steam meets point 1, it doesn’t meet point 2. On the other hand, things like the Apple App Store, don’t meet point 1, but meet point 2, which makes them more likely to fall under antitrust. Windows meets both points, which is why the US sued Microsoft for not letting people choose their browser.