Scores are as essential to dramatic movies as acting. As others have already stated, if you remove score from a movie you’re basically emasculating it. Whether the music is memorable or not, it’s constantly playing with your emotions, making you feel a certain way. Tense, sad, angry, euphoric… the heart of a movie is almost entirely dependent on its score. Very few films can function as the director intends without a score. People like Scorcese, Tarantino or Malick may not always use original score written for their films, but still accomplish the same task using songs or classical music.
So it doesn’t matter if the music is iconic or not, it is the rare score that stands out the first time you hear it (like Star Wars). Of course, it’s nice when they make for an enjoyable album experience outside of the movie, but a score’s only real job is to elevate the images it was written to.