Epic wants developers in general to have their own app stores to avoid the Apple 30%. So if Epic win, you can be sure every major developer will have their own app store on iOS to avoid Apple's 30%.
For games, it’s already like that on macOS and Windows. There’s the Mac App Store and the Microsoft Store, of course, and then you have general-purpose game stores like Steam, GOG.com, the Humble Store, and GamersGate, which is fine, because choice is good.
But now the biggest publishers want to keep all of the profit for themselves (which is understandable) and are quite happy to sacrifice their customers’ convenience to do so. If you want to play the newest games from Electronic Arts, you need Origin. For games from Ubisoft, you need Uplay. For Activision and Blizzard, you need Battle.net. For Epic or their growing number of exclusive partners, you need the Epic Games Store.
(Epic have been quite aggressive in securing exclusive distribution deals for the Epic Games Store, taking games away from other stores like Steam even after customers pre-ordered them, or so I keep reading.)
I think it’s short-sighted and ill-advised of the publishers. I perfectly understand them wanting to maximize their profit, but I don’t have the time or patience to visit a dozen different online stores to see what’s available. I’ll check out Steam, GOG, and the Humble Store, and that’s it. If a game isn’t available to purchase on one of those stores, I won’t even see it.
The same principle applies to other software. If you want to maximize your profits, make it easy for people to discover your product.