From an admin perspective:
Giving users access to the file system without the ability to fix the problem themselves by entering some keyboard ninja code is a terribly bad idea.
That being said, I feel like we'd be giving the average users a gun to shoot themselves in the foot.
Think about it like this, the average person knows nothing about computer file systems and complains that /etc is taking up a lot of room on their phone and they delete... delete... delete... to free up space, not understanding what they are deleting.
It brings poor individuals like me to my knees faster than a kick in the sack because I have to deal with ignorant relatives who ask me the same question 50 different ways and beg for me to provide my expertise which, to them, is nothing short of the collective knowledge possessed by all of the engineers who made the device. To me it's a headache that no amount of Excedrin will relieve.
I think it's awesome that some people know unix file system, as for me, I think most of the iPhone users are better off without it. Could you imagine how mad Kim K.'s iPhone repair guy would be if she had access to the iPhone filesystem and "freed up space for more selfies 3 times a month?"
File systems on mobile devices should at least require some kind of sudoing for access preventing the Jon Snows of the world from messing with both the stability of their phone and my mental fortitude.
It's Friday and I'm slap happy.