The premise is simple. If I build a city that has the basic infrastructure to where people choose to live there and you want to open a store to sell to them; you owe rent and have to pay tax. That’s how it works.
I love how people always reach for these iOS is a city, iOS is a store, analogies which often fail to adequately capture what iOS is while there is a nice little comparable product that Apple already makes. I think it's called the "Mac" did I spell that right?
All kidding aside, iOS has more in common with the Mac than it does a city, or a store, or any other bizarre attempt at an analogy that you can come up with.
Apple makes money on iOS through iPhone sales, they make money on iOS through selling iCloud, Music, Fitness, TV+, News+ etc... they make money on iOS for devs using the Apple payment processing system. The idea that Apple isn't making enough money from it's iOS IP and needs to monetize every single transaction is hilarious to me (certain digital transactions only of course because heaven forbid we scare away amazon or Walmart from releasing native apps).
The CTF is fairer but it's per download nature makes me think it will get revised at some point. I don't know why people on here could possibly defend the CTF (in its current form) after the shellacking that Unity got for trying to do the same thing with their IP. Greedy and unethical (though possibly legal) monetization schemes are still greedy and unethical when Apple does them.
Just imagine Apple monetized the Mac this way, do we really think that devs would actually put up with it? Sure the diehard Mac fans would but would MS or Adobe bother to keep building their Apps for Mac if they had to give away 15/30% of their revenue? Would any game dev bother bringing their game to macOS?
The only reason Apple gets away with it on iOS is because they have dominant market position which they can exploit. Dominance does not require them to have a large market percentage but merely that they have enough power to influence developer choices (developers can't reasonably succeed developing exclusively for Android). This power keeps devs tied to iOS as that is where 80% of the money in smartphone app sales is.
If devs could, as a collective, all stand up and say, enough, and simultaneously all leave iOS they would likely be able to drive most of the revenue that happens on iPhones to Android instead. This is a collective action problem that will never come to pass and so is of course just a thought exercise but I think that iPhone sales would crater if that were ever to happen.