The whole problem is that you CANNOT effectively serve your application which requires native functionality outside the App Store. So this causes Apple to act as a gatekeeper that can also act as your competitor who can offer lower prices, abuse their market power and/or use features on the device which you cannot. If there was an official way to sideload applications/storefronts on a normal consumers device in a way that isn't hostile towards alternative sources there would be no issue with this. (Android has the problem with hostility towards alternative sources)