Google and Apple are eventually going to lose a major antitrust suit and reform their behaviors or will be broken up.
Both companies only play this game with some of those that sell digital goods. Apple nor Google take a 30% cut from sales through apps that sells physical goods like Walmart or Amazon or sells services like Uber. They limit the practice to in-app purchases of digital content. Why? Probably because most of in-app purchases crowd are small developers that aren't as rich or organized as more traditional retailers.
Netflix and Amazon Prime Video are from huge digital content companies. Why haven't they sued? That's because Netflix or an Amazon Prime do not pay a 30% cut. Apple now exempts those companies from having to pay fees. Before Netflix received an exemption they stopped allowing new members from subscribing in-app and forced to users to a mobile webpage. Amazon did something similar even though its never been forced to pay 30% to Apple. Its initial fee was only 15%. Apple never pulled either app due to both companies skirting apple's payment system and developing workarounds.
No telling who benefits from these type of exemptions. But its becoming more obvious that Apple's or Google's tax are not fair across the board and they seem targeted at those who can't really fight back.
Eh, that’s not really what the full picture looks like. Apple has struggled a bit with how to deal with different kinds of third party products on their platform. At the moment:
Free apps = Pays nothing to Apple
Free apps with advertising = Pays nothing to Apple
Free apps with in app purchases = Pays 30% to Apple
Free apps with physical goods and services (Amazon, ebay, Airbnb, coffee shops and what not) = Pays nothing to Apple
Free apps with some kind of subscription (Not the category for Spotify et al, see below) = 30% to Apple the first year, subsequent years 15% to Apple
Apps that cost money = 30% to Apple
Free apps that offer some kind of subscription outside the app such as Spotify, Netflix and others = pays nothing to Apple
Cross platform apps = pays nothing to Apple
It’s a bit more thorny than this overview, but it’s a start. Once you sink your teeth into it, you can see how tricky it can get, and what loopholes some businesses use to get a free ride.