Several reasons why this hasn't happened on Android. Let's see a few examples:
(1) iOS doesn't let other players have their own broswer engines. Google is one of those other players, and if the iOS App Store wasn't the only game in town, they'd have an alternative pronto. Android is theirs, so they don't need to do that.
(2) iOS has strict privacy/ad rules (getting stricter too). Facebook doesn't like them. Android let's them have it - so no need to make a move there.
(3) iOS also has the share cut that Epic doesn't like regarding the in-store subscriptions thing. In Android, where this is also an issue, Epic already has users sideload Forthnite from their own store.
(4) Serious Adobe apps are not available for Android (just Photoshop Express/Mix and such lite versions for consumers), but are for iOS. So not exactly the same incentive for Above to make a move there. But if it was an option to have their own store on iOS, given their pro app subscription program, I think they'd take it pronto.
2) That would explain greater developer demand for a third party store on iOS, but not why users would seek out these more ad-intensive app stores.
3) Yeah, this would be a pretty major reason to drive third party app stores on iOS, though it's not as if there's a ton of sideloading on Android to get around the Play Store's own 30% cut, besides the high-profile Fortnite example.
4) Yes, and it would be annoying fragmentation if other major developers/publishers did the same on iOS, requiring the installation of a ton of third party app store apps and keeping track of different app store accounts.
But how many would really go through the hassle of building their own app store just to sell their products? (Maybe it'd be easier to find a way to sell and distribute their apps through their mobile browser sites.) One would suspect the number of alternate app stores to stabilize over time.
Worst case scenario, some managers decide to include an app store inside their app, they ignore the reality of the chance of success and put a whole bunch of marketing in it to their higher ups. Then they get promoted or switch jobs then blame whoever gets stuck with it 3-6 months later when it fails.
After that we'll probably end up seeing real use cases side loaded app stores (like hobby game development, or open source tools that don't want to or can't pay the Apple tax).
Epic argued in court that Android side-loading has been designed to make side-loading difficult and annoying.
Background, https://en.wikipedia.org/wiki/Epic_Games_v._Apple.
There are many big players that don't go through the Play Store, and for a variety of reasons. Fortnite and ISP-promoted apps and device-manucacturer apps (for business and leverage reasons), DMM (because a primary line of their business is in adult content), and basically everything in mainland China (because Google doesn't operate there).
These players all operate their own app stores.
But ISPs still deliver apps through their app stores, and whole segments of big players also successfully distribute outside of it, out of necessity: adult content and the Chinese ecosystem. Note that the DMM example I cited is unheard of outside of Japan, but very well-known in Japan itself.
I’m genuinely curious. I have no clue.
The app store is just called DMM Games store [0], since it distributes both its age-unrestricted games as well as games under its adult imprint (Fanza) via it.
With videos, since stores of videos are allowed on the play store, you instead have the situation that the DMM videos app is available on Android and iPhone, and the Fanza imprint is separately downloadable on Android [1, nsfw, needs vpn]
>Users would have no recourse than to install the app for there (or do without Facebook or Zoom etc).
We are already aware of a platform that allows easy sideloading - Android. And most apps on Android are distribured through the Play Store. All "big" players still go through the Play Store.
When there is no such thing as the examples you described going on in Android, why do you expect iOS to be different?