As an user of an iPhone I don't want this. I bought an iPhone because I deal with enough technology in my day to day job and I want a phone that's straightforward to use and doesn't need any attention. So no I don't want to install three app stores on my iPhone and have to deal with 20 different payment providers.
In the end it's important to make the distinction between consumer interests and the interest of businesses that want to sell their product on the iOS platform. I get that this sucks for developers because iOS is from what I've heard much more profitable than Android. In my opinion consumers interests should be weighed higher here and Apple's policies for the App store are mostly pro consumer, at least compared with the situation on different platforms.
Consumers that want a more open platform can always choose Android or Linux phones.