Because that’s how selling stuff on third party works.🤣 You'll have to tell me why you think Apple deserves a 15% cut of Netflix's subscription revenue when Apple isn't producing or hosting the content.
Interchange fees? The average interchange fee is between 1.5% and 3.5%.
Xcode software to develop for Apple and the App Store? The cost to host the app on the App Store? That's what the $99/yr developer fee covers per https://developer.apple.com/programs/
Join the Apple Developer Program to reach customers around the world on the App Store for iPhone, iPad, Mac, Apple Watch, and Apple TV. Membership includes all the tools, resources, and support you need to develop and distribute apps, including access to beta software, app services, testing tools, app analytics, and more.
What else is there that Apple is providing and should be compensated for?
If I were to sell your product at my shop, I would expect some form of commission from selling your product. Say 10% to keep it fair. You get more exposure for the product you made and you generate profit from sales by selling at my store.
You can’t expect me to sell your product and I get nothing. I’m not running a charity. It costs money to run the shop selling your product.
Same with Netflix trying to do business with Apple via App Store. Latter aren’t running a charity shop. They are business. They expect to take commission because running a business to sell a third party product costs money.
Nothing new here. Common business practice.