Here is a question I have not seen a satisfactory answer for. Why is having an App on iOS a must have? It seems like any discussion about the market fairness of Apples policies requires a shared understanding of how necessary the ecosystem actually is. If you can freely choose not to deploy to that ecosystem then you can vote with your "wallet" so to speak. If you can't freely choose however then there is an argument…
Because iOS represents about +60% of the revenue in the global mobile market, probably even more in some countries where it has a bigger market share.
It's naive to think a business with a product/service can just decide to not have a presence on iOS.
It's not even completely about the iOS revenue either, but the simple expectation from users that a service has to be on as many platforms as possible. For example, I wouldn't be a Spotify user if I couldn't use it on all my devices.