"How is it fair for Price Chopper to undercut Rice Crispies with a similar, cheaper product?" no on says this...
If we go with the store=phone analogy, then somehow my brand A flour and my brand B milk are magnetically repulsed and I can't make pancakes. It's not good for consumers.
Before you should people should simply switch phones: you can switch phones, but you can't take the apps you bought with you. And even if you switch: there's only one real alternative: Android. If Apple is allowed their 30% cut on literally everythig, why wouldn't Google do the same?
This way you end up with only 2 App stores, 2 Music and 2 Movie streaming services.
We do have only two app stores. Apple and Google just haven't managed to kill all the competing Music & Movie services. They'd love to!