Why would someone who wants to hack their device buy an iPhone?
It is well known that Apple tries to make this difficult, whether you believe that it is about offering more security for it or more revenue for Apple is irrelevant, this is what they do.
You can buy Android devices that make rooting it and replacing the ROM simple, and when you get down to it the underlying hardware in most modern smartphones is pretty much the same. Buying an iPhone with the intent to hack it is like buying a Chevy with the intention to stick a Ford engine in it. Sure, it can be done, but you're knowingly making things difficult on yourself without a good reason to do so.