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,

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.