[asr]

Your question is worded to suggest you are not actually open to the answer, but I will try anyway: in antitrust law. You cannot create an open App Store ecosystem, invite in outside developers, and then pivot and kill them all off by steering customers to your own app. Closing off your previously-open ecosystem can be illegal. Read Eastman Kodak Co. v. Image Technical Servs.

[supernova87a]

I am open to explanations. I'm especially interested in how a phone manufacturer that is 3rd place among others can be said to have a monopoly over the market. Or do you mean just for iPhone apps? Because at that point, how fine do you get to dice it to find a monopoly? I'm sure that once you slice it thin enough, almost any company can be said to have a monopoly. Where does it end? Joe's Pizza has a monopoly on the sale of pizza on the 300 block of Main Street, and has been trying to keep out competitors by buying the store next door.