I have several friends who used to work at Valve none of them hate the place, they still have friends there, etc. But they tell similar stories as to why things that normal companies do successfully are impossible at Valve. Perhaps it’s best summed up by something one friend said about her year and a half at Valve: “I first learned who my boss was on the day she fired me.”
Google tried this, notoriously dense grating and then firing basically all the managers at an all-hands. That didn’t work out well at all... And now they have over-steered in the opposite direction!
There is a strong sentiment with many gamers of just not wanting to use an alternative and it is basically a non starter for many other stores. Many complain about the very idea of not all of their games being in the same place.
This isn't necessarily anything monopolistic done on Valve's side. But it would be very hard for another store to make any meaningful impact regardless of how they are.
I’ve met countless gamers who will simply not buy or play a game if it isn’t available on Steam.
Myself included, and all of my gamer friends.
There isn't a cost to having multiple stores, you don't even need to keep them running at all time. I get the concerns over the Epic app, but Heroic exists.
Personally I have games on Steam, Xbox (cross buy between xbox and PC), Epic, and EA. Plus Game Pass.
The only annoying part is when I go to install or buy a game, finding where I have it or making sure I don't already own it somewhere. But there are launchers like Playnite to address that.
But it does feel like I am in the minority with this opinion.
I tolerate steam on my laptop because they were the first. I hate Epic and other launchers when I just want a game.
I will wait until it gets to steam. And have even skipped free games because I don’t want the mental load.