Personally as someone that pays 50%+ of my monthly income for my government subsidized apartment, I don't think mobile apps should be the priority.
It seems like most proposals from companies actually making money on the platform (as opposed to folks like you and I in the cheap seats) are to keep the experience the same for the users, with the same amount of value, only charge less.
Where's my 30%? Because the value I provided was critical to that transaction, to that experience, to the value provided. Others could have provided that value, but didn't.
I can make the same argument you make. But I'm not a trillion dollar company. That's the real difference.
Stores can then actually compete on merit.
See that's the thing about actual competition is a price can be determined by the market, especially in the case that you have many players rather than a duopoly. In my case Apple could charge whatever they wanted, 30%, fine. But me the app maker could go to the A+ store and pay 10% instead.
Obviously this is wishful thinking, but given how smartphones are a mandatory part of our social life, stores being a public service would make much more sense.