Why do songs disappear from Spotify?

Related questions

1. What is the most listened to song on Spotify?
2. How do you upload music to Spotify for free?
3. Is listening to music on YouTube considered Streaming?
4. Does Spotify or YouTube music use more data?
5. Do live streams stay on YouTube?
6. Is streaming music free?
7. What's the difference between Google Play Music and YouTube music?
8. Why are some songs not available on Spotify?
9. Is Apple Music or Spotify better?
10. Who has more users Pandora or Spotify?

Tags

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2. #world
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4. #music
5. #artist
6. #wants
7. #reason
8. #disappear
9. #availability
10. #decided
11. #playlist
12. #happen
13. #likely
14. #their
15. #making
16. #songs
17. #remove
18. #spotify