If apple is able to prevent users from doing things they want to on a device, that device belongs to apple and not to the users.
- a moral perspective
- a legal perspective
- a "might makes right" perspective
Because all of those are different things. People are not saying that they practically own an iPhone in the sense that they control it; they are saying that they are the moral and/or legal owners of an iPhone and it's messed up that Apple is still allowed to exercise a "might makes right" kind of ownership over a device that the user purchased, essentially overriding and stealing ownership back from the user.
Be cautious about talking past each other in these situations. Apple's exertion of control is the thing people are complaining about here, and that exertion of control is not a legal or moral doctrine that dictates whether Apple should have that control.
If I get sued for stealing someone's car, and I tell the judge, "but it's not his car, it's mine. Look, I have it and I have the keys and he doesn't and I can drive it and he can't, so by definition it belongs to me", well... that's not an argument that's going to get me very far legally with that judge even though technically, sure, that is a definition of ownership. I don't think if Apple ever gets sued for antitrust the lawyers are going to be arguing, "but the consumer doesn't own their iPhone because we can remotely brick it, so by definition we own it." Again, not wrong, that is technically a definition of ownership. But it's just not what people here are talking about.
Users owns the device. Why would you think Apple does? And Apple forbids users from using devices that the user owns in ways that the user wants to. Why are users forbidden from programming html rendering?