Sure, that sounds fine on paper. But the problem would be that you can't install whatever you want on your iPhone. So iPhones would have to drastically open up

Sure, that sounds fine on paper. But the problem would be that you can't install whatever you want on your iPhone. So iPhones would have to drastically open up before that becomes some kind of utopia. We want a future where people own their hardware, and going to a phones-only world currently wouldn't be a move in that direction.