What's great about tracker music is that it's in source format, readable, editable and remixable as if you were the original author.
Open source music! Great for learning.
Yeah, that was a nice side effect - but only a side effect. The real reason why the music was released in this format was space saving. If you would have wanted to release a song with all the tracks already mixed together, you would have had to store it as an uncompressed or losslessly compressed "waveform" file, and a very modest song would already have filled up an Amiga 880 KB floppy disk all by itself. Contrast this to Lemmings, which had not only ~10 songs, but also the sound effects, graphics, game code and 120 levels (although some levels were 100% identical to earlier levels, just with a tougher distribution of Lemmings skills and/or higher quota of Lemmings to save) on 2 floppies...
Object based audio... but 30 years earlier.
I had so much fun replacing all the samples of my favorite mods.