> So why is it OK for Amazon to get a fee, or any physical retailer? Aren't they unnecessary middle men too?
Amazon or Walmart or any other online or offline super market doesn't prevent either the manufacturer to sell directly to the consumer, or me as a consumer to directly buy from the producer / manufacturer.
Apple does precisely that with its restrictive app store on ios (and soon will on the macOS too), denying the buyer the right to buy an app directly from the developer and avoid the unnecessary burden of the Apple Tax. Due to this same restriction it is also able to charge the developer an annual recurring fee, again unnecessarily raising the total cost of an application for the user.