This is perhaps my least favorite thing about Apple's software concept, but at the same time I have to admit they've made it simple for the masses, and it works. The iOS file concept seems to be closer to how people without knowledge of computers perceive things, and matches what I saw in computer learners 20 years ago. People would think their documents were gone if they couldn't launch Word, or were confused by getting a file on a floppy that they couldn't open because they didn't have the right program installed.

Technically, you have a generic filesystem, and individual programs can load files from that, there's no direct relationship between the files and programs. But in the mind of a typical non-tech user, files are something that belong to a program.