Depending on how it was done, they might still have to go through Apple. But China/Iran/Russia/whereever could say: "You did it for the FBI, so you need to do

Depending on how it was done, they might still have to go through Apple. But China/Iran/Russia/whereever could say: "You did it for the FBI, so you need to do it for us, too." And the FBI could say: "You did it in that last case, so you need to do it in these other cases too." And every local podunk sheriff in any jurisdiction could do the same thing, and there would be no end to Apple having to fight these things or do this work. Not to mention that its customers would start getting harmed in countries where leaks of your private information can lead to your death.