Of course you were in the third category, since it was the only one you didn't describe condescendingly, in a sardonic and paternalistic way. Figures. The "mature audiophile".
I'm probably part of the fourth group of people, the ones who "are missing out on such great music". Yeah, I can't really listen to video game music outside of the video games, unless it's something particularly different, like Grim Fandango's or Outlaws' soundtracks. I liked Tiny & Big's OST, too, since it was actually indie rock with some indietronica tracks, made by actual artists, instead of just some dude composing "orchestral EPIC music" that sounds like every other piece of "orchestral EPIC music" used in film or video games. I enjoy listening to it in the games, but I don't see the point of doing so while working, going for a walk, grabbing a smoke or reading a book at the corner café.
In the off chance I do listen to a soundtrack outside of the game (I particularly enjoy Jessica Curry's works, including her astounding Dear Esther OST), I'm also a "plebeian" about it, because I tend to listen to all my music in MP3 format. I'm not exactly young, even though I'm not particularly old, and I never managed to "move on" to the whole music streaming scene, I like to have my music files on my devices, and I mostly listen to music on my Creative ZEN Mozaic, which has great sound playback but, unfortunately, doesn't support FLAC or other lossless formats, including most, if not all, of the native formats you mentioned. I do buy most of my albums on bandcamp (yes, bandcamp also sells music that isn't video game OSTs -- shocking!!!), and they all come with FLAC versions, which I keep in my PC, but it's just that I don't listen to that much music on my computer.