That's the problem, apple forces you to use the apple app store if you want to sell digital goods for the iPhone, then takes a 30% cut.
Why do you want to sell digital goods for the iPhone? Oh, I see. Since the turn of the century, Apple has spent $183 billion on R&D, and over $226 billion getting its products marketed and sold. By doing so, they have built a base of loyal and affluent customers who trust Apple to deliver quality products and services. You'd love to tap into that customer base without having to spend the $400+ billion over decades, wouldn't you? We call that freeloading.
Try telling Walmart they must allow you to set up shop inside their outlets and bear all the expenses of warehousing, delivering, payment processing, etc., yet make zero profit from the activity. See how far from Bentonville you land when Walmart boots you out of their office.