Because their current behaviour is anti-competitive rent-seeking, and limits innovation.
Anti-competitive by mandating use of their products, rent seeking because 30% is absurd (but alas legal), and as one twitter thread pointed out, if the web hadn't already existed, no existing web browser could possibly have passed Apple's app store policies.
I guess I don't see them mandating the use of their products. You can have your app on iOS or not. I just don't see the moral issue here. They've never raised the prices and have had this price since they had 0 3rd party apps so I have a hard time seeing it as rent seeking. Do they make a lot of money? Yes, they do, but is that enough to force them not too? I'm just not convinced of that yet.
Apple are mandating the use of their Apple ID and Apple Payment System (aka products). The first might have a security rational, the second does not, yet devs must pay Apple's fees even if they are higher than alternatives[, a defacto price raise].
It used to be possible to get payments on iOS going without using Apple's payments, before Apple set their eyes upon that market.
Anti-competitive by mandating use of their products, rent seeking because 30% is absurd (but alas legal), and as one twitter thread pointed out, if the web hadn't already existed, no existing web browser could possibly have passed Apple's app store policies.