When it works, it is impossible to hear the song without thinking of the film. Kevin Costner dodging bullets in The Bodyguard. Will and Tommy Lee Jones saving the world from comedy aliens. Trainspotting started it all, in 1996. At times, both films could be mistaken for a collection of pop videos.
Some soundtracks have greater longevity than some pop stars.
And some sell a great deal more than pop stars. Compilation albums are fast becoming more popular than traditional CDs. A soundtrack can do wonders for a young band's career.