For the most part the reason albums and music disappears has to do with the artist or label and not spotify themselves. Sometimes it is a marketing tactic or because the contract expired why artist remove music off spotify. But there are mishaps where there have been technological errors or malfunctions. I suggest that you could reach out to the artist or label company why a song or album isn't on spotify.
Sorry that you are unable to listen to some of the music you wish to. I hope I cleared something up for you and that you will be able to find the direct reason why you aren't able to listen to those albums. Have a great day!