Steam is a bit of a very special case and I think very different from either Apple or Google stores.
Steam is never part of a platform, except for maybe the steam deck, and even there it lets you very easily replace it.
Steam will install other stores automatically for you. Does the game need EA's origin or what ever the epic store is called? It will install it as part of playing that game. Users will have multiple stores installed and will continue to choose Steam.
In the case of Apple or Google, I'm given a store forcefully. Google let's you jump through hoops to get another store but it isn't easy.
To even get Steam, you as a user have to make a very conscious choice to install it.
Steam is very much the choice of users and even many developers.
Steam is a private company and doesn't seem in the business of ever attempting to screw with or limit users.
Hell, Steams development of wine/pronton is the explicit choice to give users more choice.
Steam maybe an app store, but IMHO it is definitely not ever forcing anyone to do anything, unlike Apple or Google.