Earlier quoted context omitted.
Sometimes Spotify swaps them for others by the same artist. One of my favorite instrumentals got swapped out for the version with vocals which I can't stand. I can't for the life of me understand why it could be a licensing issue.
It's a multilayered issue: - licensing could be expired, could change hands, could be removed, could...) - naming and attribution: A single song by a single artist will have a gazillion versions (ep, lp, original, re-recorded, re-released, re-mastered, re-re-mastered, best hits, best songs, essential, released for the European market, released for the Japanese market, Christmas special...). On top of that distributor…
Because all of the above doesn't even begin to deal with things like territorial restrictions, content restrictions, territorial content restrictions, territorial content requirements, take down requests from commercial and government entities, rights disputes, content embargoes...