> Until other companies also move to a third party App Store. Why wouldn't they?

While I don’t know the exact reason, this isn’t what’s happened on Android, which has always allowed multiple app stores. Everything mainstream is on Google’s Play Store, and quality FOSS apps get published to F-Droid. My theory is that users shy away from sideloading alternative app stores, even if it’s not very difficult to do so.

I think it's because the Google Play Store allows the behavior that Apple is banning, so why bother?

I don't think users would shy away from mainstream apps like Facebook if they moved to another app store platform.

The Play Store takes 30%, in addition to their own set of restrictions. Surely 30% must be a large motivator for some mainstream apps moving to another store - it just turns out few users on Android will go for that.

Why would Facebook care about the 30%? They care about being allowed to track users (as Google does).

Because 30% is big money. FB might be able to compensate enough, but plenty of apps can't. There should have been enough pull to have a SpotifyStore and an UberStore, or even a SpotifyUberStore. Yet it doesn't happen at all.

What is Google charging Facebook 30% for? In-app transactions?

Everyone will still have to use Apple's store, especially given Apple PR makes sure to promote a cult-like adherence to anything Apple. Even fortnite couldn't survive outside the Play Store. It doesn't happen on Android, why would it on iOS?

The only thing a 3rd party store support will do is to ensure Apple couldn't abuse FOSS apps too much in their review process.