Honest Question
Because I don't know a huge amount about the workings of an iPhone. What would stop someone ghosting the storage of the phone? If that's possible then why would you not load the image into a phone emulator and try the 10(?) combinations before the ghost wiped itself then reload the image into an emulator, try the next 10...you get the idea. I'm guessing there's something that would stop that being possible because if I thought of it then I'm sure some clever whatnot in the FBI could and all the forcing Apple to do something would be about something entirely different from getting hold of the information.
Rosie