As a movie and music buff, I like to buy soundtracks to movies so I know what music to expect in the movie. In many cases, most of the best songs on soundtracks were not played until the end credits started. If the soundtrack is mostly composed music with one or two songs on the album, the song(s) are definitely going to during the credits. Take, for example, “Love Song for a Vampire” by Annie Lennox was on the “Bram Stoker’s Dracula” soundtrack and it did not play until halfway through the movie’s end credits.
Here are some more examples of end credit songs:
Pop Culture Redefined 