Because music has a tendency of suddenly disappearing on Spotify. Either labels decide Spotify isn't giving them enough in return, or artists are angry at Spotify for their stinginess or because they have a podcast which they disapprove of. Look at your playlists that are over a year old. If you are like me you'll see that 10% or 20% of the tracks are unavailable now. This is the downside to streaming -- nothing is permanent.
I was thrilled when I read Spotify was coming to my country. Then the main genres I listen to (Reggae and Dancehall) have many tracks unavailable as the labels (VP Records is the worst) whitelist countries. I reverted back to local files.
