It's not. People attempt to justify it by claiming "you will make more money if you sell on iOS", but there are plenty of Android-only apps that are doing just

It's not. People attempt to justify it by claiming "you will make more money if you sell on iOS", but there are plenty of Android-only apps that are doing just fine. At any rate, just because a platform is popular and will make you more money doesn't mean you have a legal right to force that platform owner to do business with you. (Unless it is ruled as an "essential facility", which is what Epic claims, but I think is a huge stretch and not likely to be accepted by the court.)