On a PC in order to access every game you need to have Steam, the Epic store, the Microsoft store, all these stores... argh! You want game X? Only on Store A. Game Y? Only on Store B! What a pain for no reason!
This is a problem because each of these stores use their own proprietary client. If instead they all used a public API then there could be an open source client that can access any of the stores.
We of course already have a possible client: the web browser. It works great for all sorts of e-commerce sites. It just doesn’t work for installing games from these stores. That could be changed, though.
I think if Apple is forced to open iOS to alternative stores, then I would like to see an API based approach. Force all the stores to compete within the same app, so they’re only competing on price and selection.