That’s exactly what is happening on PC gaming right now. Every game comes with it’s own AppStore (or similar bunch of extra software).
I’m torn on this. I do agree with users having more choice, but I also see the huge value of Apple being able to protect user’s privacy and security by having a tight control of the AppStore.
If my understanding of the history is right, that's how Steam was born. A unified update tool for Valve's games. It was pretty cool that all my Valve games were managed in one place! "I wish every company did this!". While it was nice that there was really only one primary place for games (Steam) for a while. And it's really nice when most games can be acquired in one or two places. I think the landscape has changed and "download managers" and their glorified counter part "app stores" are much more common... at least the worst case scenario is what I once wished... "Every company/publisher has their own App Store"
Just my two cents.
I've said this before: if Epic wins the lawsuit, you're going to either see the Epic launcher show up on Xbox, Playstation, and Switch or Epic's going to 'negotiate' with those publishers to get an extra 15% (or more) cut of sales.
Having different stores also forces these publishers to be more creative to get people on their platforms, see the weekly free games in the Epic Games Launcher.
If there was no competition, there wouldn't be the possibility to buy DRM free games on GOG for example.