It's from a time when the media was so small there was no need to categorize anything because the entire directory listing fit on a single screen in most cases.
Stuff ended up being characterized by what disk it was on (floppy labeled "homework" vs. "games") rather than where it was in a filesystem. Directories were only necessary once Hard Drives appeared and you could centralize your storage.
And now we're kind of coming out the other side, where storage is so large and can contain so many items that organizing it all into a hierarchical structure is a full time job in itself.
MP3s can mostly sort themselves, but your pictures ... and then you have the N-layer-deep "old computer" directories, where you copied all the files from your last computer to your new computer.
These days every desktop environment integrates an increasingly featureful fast search feature front and center because they know you aren't going to be able to keep up.
It was hard to understand hierarchical file systems if you started out using non-hierarchical file systems. I write from experience using Acorn ADFS on the BBC Micro. You get into a way of working with what you have.
With ADFS the files could be put in directories but these were single letter prefixes to file names. You could not change into a directory and, once one's mind was thinking the ADFS way, the idea of a sub directory with further sub-directories was as conceptually difficult as it is to imagine what 5D space looks like.
The way regular users save files to the downloads folder or the desktop with no sub directories is different. What they are doing is quite sensible for their workflow. This is an extension of 'search don't file', which is Gmail ethos for what to do with your mail.
In previous times 'search don't file' wasn't viable for email. You had to create rules and sub folders. Gmail enables you to do that but it is productive for people who don't do that due to the search.
Traditionally Windows was useless for finding files with search, taking too long and showing you some cartoon dog whilst it chuntered through files slowly, with no command line 'grep' power tools. So you had to 'file' rather than 'search'.
ChromeOS and Android are 'post files' systems to an extent. ChromeOS has moved on from desktop computing of old. I am not one to knock casual Windows/Mac users that 'instinctively' work the ChromeOS/Gmail way. Of course I would hang, draw and quarter any programmer that didn't save files the UNIX way, i.e. in folders with no spaces or other weird characters in filenames.
