.mod is demoscene stuff... oldschool Amiga roots.
Rippable, editable, fits in your pocket – unlike MP3 renders of the same which are several times the size and all one piece (and usually, missing all the original comments, too)
As for mp3 vs m4a vs wma vs ogg vs whatever, I couldn't give a crap about that, they all sound the same... Actually I've seen double blind studies that suggest m4a is supposedly better at lower bitrates and blah blah blah donkeynipple, but I'm not a engineer or anything so I don't know. Who knows, Apple probably paid them off, but I personally can't tell the difference and that's all that matters.
Btw, I have a desktop running XP, a laptop with OS X, and another Linux desktop, and I also run a web/torrent server with FreeBSD on it. I use them all pretty much equally, and they all do what I need them to do. So before you start labeling people, take a moment to think about what you actually know about the person on the other end of the network cable. Sometimes you can make assumptions and they're more or less correct, sometimes you can't and end up looking like an asshat. Best to save face.
tl;dr shut up and post more music