Let's go back to Desktop OS. Right now, and since inception, if you wanted to download an app on your PC, you can goto a developer site, MS app store, retail store, online stores, etc. You have MANY options to distribute your app. WIth iOS, you have 1 option, AppStore (no sideloading, etc., less consumer choice).
What if MS had Windows locked down just like iOS, and every app had to list with the Windows app store and pay 30% fee.
That means, Apple prior to even the iPhone, would list iTunes on the Windows app store, and every song that was downloaded from iTunes would have 30% paid to MS, and even with launch of iPhone, every app download iTunes app store from your PC would pay 30% to MS. Crazy to think about it, right???