The relationship between music and film...

The problem is not the use of songs in a movie (Scorsese is one of the masters of setting the right tune to the right moment), but the availability of the music. You need to get clearances and the use of existing songs can be very costly. You might not be able to get the songs you want.

Though I have not hated any of his films as others have, Wes Anderson is getting a bit jukebox-dependent. And between his song-scoring and TV/film quotes, Tarantino is more of a DJ these days.

I'm curious as to whether or not you think this is a problem

If you are ever planning to sell said script, it would be wise to clip out any references to the music in the text of the copy your are sending out. I wrote a script for a class once which had a complete soundtrack listing of 10-15 songs (yeah, I know). My professor advised me to remove the songs (I had put the song titles in the script with their corresponding scenes) because if I shopped the script, a producer would just see it as a script with an extra pricetag because of music licensing. In most films, song-based soundtracks are usually an afterthought (post-production money). Of course, there are exceptions, and you really should hold on to your track list so you can work with it in case the project does get made.

Haha Morbs is so right. When I first started working on my own scripts I fell prey to the whole song dependency issue. I've since realized I much prefer orchestral scores than soundtracks. Also, if you use older composers you don't fall into the whole licensing issue.