Not every album or song is available on Spotify. Some artists and music labels choose not to release to Spotify.
The only thing Spotify does is upload the music that is sent to them. You can find out why some songs/artists are not on Spotify over here.
Some music labels only release to certain countries while blocking the release from the rest.
It's all about who owns the rights to the music and where they want it released to.
Music would be better if labels didn't block their releases from certain countries, but sadly this is how the music business works.