Who is honestly going to buy this highly sought-after iPhone, backdoor it and flip it for a discount on Craigslist in an attempt to what, hack a random person? And you can just prevent that by doing something simple like disabling the App Store…

First, my argument only applies to when these are common and not highly sought after (see the top level comment I replied to). Not necessarily a random person, but having an easily obtainable rooted iPhone would absolutely enable targeted attacks against wealthy/famous people.

Think of it like a classic USB drop attack but a bit more expensive: you install your remote management code on a phone, box it up like new, and drop it at the door of someone wealthy's house. I'd bet they would happily assume it's a wrong delivery and start using it if it's an upgrade over their current phone.

Again, if you make the research iPhones unmistakable people will figure it out. And yeah, people ignore strange markings or click through warnings, but if you make it impossible to do the thing they want to do then they literally cannot ignore it.

I agree with the first sentence, but disabling the app store would greatly hamper security research, since you can't debug third party apps.

You'd just download the IPA manually and self-sign it or whatever. Basically just make it unmistakable that this device is not normal and block normal people from being able to use it as normal without realizing it's a development device.