Why do you have to purchase a full album to get certain tracks?

Good question! Though the vast majority of tracks are available for individual purchase,  sometimes a song or songs can only be acquired through the purchase of the entire album.  Certain labels prefer that these tracks—designated as “album-only”—be available only when you purchase the full album. Also, tracks above 10 minutes in length are by default Album Only tracks.  Soundtracks also often have many Album Only tracks, because they normally include songs owned by many different labels, making licensing more complex.