I don't think so. I'd say the mobile market is quite different. Look at Android and the Google Play Store which also has similar pricing stipulations. There are players offering separate app sources/stores (Amazon or Epic appstores for example), but I certainly wouldn't consider virtually every big player or even a large portion opting out.

Google is less restrictive than apple leaving less reason to opt out.

No they wouldn't. See the Google Play Store.

Do you know that Epic failed with their Android Epic Store because no one was sideloading it from their website and quickly went to the Goole Play Store and started paying 30% fee because users use unified solutions not geek ones.

See Android.

It shouldn't be called "Sandbox"

Which is exactly why Apple users specifically do not want third-party app distribution at all.

This isn't just blind fanboyism, either: PC gamers absolutely loathe Epic Games Store and the Microsoft Store, because they want their entire collection of software to live on Steam. Yes, a decade and change ago everyone hated Steam, but now it's the established way of doing things. The more developer-friendly, competitive option is to have 15 different launchers, one for each publisher, with their own payment systems, terms of service, and so on.

You can see this in the reactions Apple users have to the Epic lawsuit, versus their reaction to stories of Apple demanding their cut from developers that don't have it to give. They're way more sympathetic to companies that aren't trying to split their app libraries in half.

(EDIT: I should probably clarify that I, myself, don't think alternative iOS app stores would actually take off without major cross-subsidies from powerful industry players. Google Play has a stranglehold in markets where it's available, even though Android has no technical lock-out like iOS. EGS on Android is a joke and I would never install it. On the other, OTHER hand, though... Android in China, where Google Play is banned, is basically PC digital downloads, pre-Steam.)

This is you really liking the mall experience where stores are paying twice as much rent to be in the mall and trying to make it illegal for shops to do business outside the mall to maximize your shopping experience. You and the mall are both in love with the idea.

If you want to shop in the mall vote with your wallet if there isn't enough demand to convince merchants to situate themselves there then deal with it.

Laws forcing merchants and customers into the mall ought to be themselves illegal.