Plex has very little setup to make work. And the fancy front end has an option to view by folder structure.
I'll preface this by saying I haven't used Plex in a couple years, so maybe things have changed:
Back then when Plex scanned your library, it would look at the folder structure and filenames and go to a TV/Movie DB to pull down metadata for fancy covers and episode descriptions. Which is all fine and dandy, but if it wasn't able to find a match on the DB for a particular file, that file would not be listed when you were browsing your library. Even in the folder view. Not to mention all the things it labeled incorrectly.
At the time, multi-season shows had to be given specific names, put in folders a specific way, the folders had to be named a specific way, it was a hassle. Alternatively, the folder browser on the PS3 "just worked", and I didn't care about it looking pretty. The point is to stream content, not look at pretty menus.