Valve had a 17 years or so time to develop a launcher b4 Epic entered the market. And even if their laucher would be bad, its just where the people are, where they have their collection, they do not want to leave it. Its actually not such much about how good Steam is, its about the time advantage Valve has.
And of course they have the better launcher. But now they are soo big, and they have such a de-facto monopoly that Epic had to go to extreme measures to get some market share. And that is using Fortnite kids parents money to give out free games all the time while actually paying the devs for the games and pay massive amounts of money to devs for exclusive deals. Its all money they have from Fortnite and (Chinese) investors. That also sucks but its better then just one store in town. Bethshitsda has given up on their own distribution and they are back 100% on Steam and they just suck it up and pay the 30% because they failed to compete, no surprise there.
I actually think the situations are pretty similar. Except that there is not even a open door to try to compete with the Apples Appstore right now. But they both take 30% and everyone is basically forced to pay it. Game devs can not just release on Epic. They must release on Steam and they must then pay 30% to Valve. If you release a mobile app you must release on Apple and Google play and they take 30%, its the same thing. Even thou there are other stores like Amazons shitty store you are just forced to publish on Google/Apple.
I just hope one day decentralization is so mainstream and consumers just buy from creators directly or some blockchain or something without a gatekeeper middlemen that sucks 30% off.