Compilation Scores

I was walking down the street the other month, with the Rolling Sones 'Gimme Shelter' playing in that horrible loop your mind does from time to time, when I realised how wonderful a piece of pop music it would be to use in some kind of suspence driven, crime genre film or television show. I felt understandably foolish when I watched 'LayerCake' a second time to find that it had indeed been used just so. It had also been used in a much more stylish way than I myself would have ever envisioned. What I was musing on was on the possibilities or scope of the compilation score with reference to pop music. Films such as "The Big Chill', 'The Big Lebowski', and 'Boogie nights' amongst others all have powerful amounts of hit pop tracks in their scores. I was interested in the particular genesis of the score's creation, in general. Do films like these have such scores because A.) it ties in with the horizontally integrated other arms of the parent company B.) because it helps the sense of atmosphere/feel of the film (i.e the 70's/80's of boogie nights) or C.) other reasons, such as Wong Kar Wai's 'Chungking Express' where he revealed in an interview that before he had fully thought out the plot (two narratives about police officers love lives that are joined into a single film) He had already decided to base the film around The mama's and the Papa's song 'California Dreaming' with the various parts of the song portraying the various moods and mindsets of the protagonists in the film. Which is interesting but by the sixth large repetition of the song as a leitmotif bordering on pretension.
Has anyone else got any other general Ideas for new/old reasons of Including popular tracks in film, note they don't have to be nearly as general as mine.

Cheers.