Imagine that you lived in a town where there was only one grocery store, from one company.
You live in a house in a town and every one to three years you move into a different house. All your stuff is transferred automatically by movers when you move. In the town you currently live there is only one grocery store and there are only a very small set of house designs built by the one company that also runs the grocery store. That same company also provides police protection, television service, a gym, a bank, messaging, mapping, news, games, and other services, all tightly integrated.
Whenever people say there should be more grocery stores, you tell them to move to a different town where there are multiple stores.
Whenever people say there should be more grocery stores, you point out that they moved into that house, knowing there was only one grocery store, and that one of the reasons they wanted to be there was that the grocery store was better then the many grocery stores in the town next door. However, if they no longer feel that way, they can move when they normally would (when their house expires in 1-3 years), to one of the much larger variety of houses in the other town, and take advantage of all the various services, developers and companies that the other town offers. It will be super easy, as you move into a new house on a regular basis anyway.
You say people should have the choice to live in a town where there's one store, because it reduces the risk of people buying low quality or even poisoned food.
You argue that the planned community with the tight policy protection and tightly integrated services should be an option for those who want it.
Ask yourself honestly: could or should such a town exist in the USA?
Yup, there are many such towns in the U.S. They really do exist. They are planned communities, retirement/assisted living communities, and single developer housing developments.
And more importantly, is such a town normal in any way?
Yes, very normal. Often, just like iOS, people pay a lot more to live in this style of development. Gated communities are often the most expensive places in which to live.
Would it not make much, much more sense to simply chose to use that one store if you trust it so much, regardless of how many other stores are in town?
Not if by having multiple stores, I have to create accounts in many different stores, sharing my information at all of them. Not if I have to give up the level of integration as that would be prohibited by the same system. Not if it would mean that I would have to give up my privacy (as you can be sure that those who want to sell my information will only be available in the other, less scrupulous stores).
There you go. I have given an analogy much closer to the reality in which we live.