Is it possible for us to have the original soundtrack as a downloadable goodie? Or I assume there is some kind legal reason it can't be. I remeber the original game box came with a disk containing the sound track.

Possibly because of royalties or/and legal thing. If you truly want the soundtrack, check this post on how to extract the music from the game files:

https://www.gog.com/forum/titan_quest_anniversary_edition/ragnarok_ost/post3

Yeah, extracting is your best bet. Anything official also only contains the main tracks and nothing else. There used to be a complete soundtrack containing all music extracted straight from the game files (TQ+IT) on Youtube and it was nearly 4 hours long IIRC. Anything official doesn't even reach 2. The video was removed sadly.

There is Titan Quest Soundtrack on SteamCDR according to steamdb.info site (and it be for re-released TQ:IT steam-version, not Gold but still before Anniversary released) - but it never be completely\released.

So yeah, probably some legal problems appear and it never be available.

But at same time - as always - this is publisher lazyness as well. They didnt release OST for AE\Atlantis as well. Only Ragnarok.