This is why monopolies, or as the case may be duopolies, are bad. When they launched their app stores, nobody argued against the 30% commissions, because it was a smallish market. But the market has ballooned, and at some point they were making money hand over fist, and the 30% commission was becoming disproportionate. With a market functioning properly, rival app stores would have been created with smaller commission fees, and eventually they would have had to lower theirs as well to stay relevant. But since nobody could create another app store for the iPhone, and even for Android the starter advantage of the play store was overwhelming, they never had to do that. If anything, they have become more strict in grabbing a share of everything that was getting paid through their platforms.
So now, countries have to intervene to protect competitors, and the users who are ultimately paying for the fees.