Why are music in horror movies usually not in the soundtrack?

Question

Take for example Resident Evil 2: Apocalypse, there are songs like 36 Crazyfists - Bloodwork and Lacuna Coil - Swamped which are not even in the movie....why is that?

Update:

Hey Shadow, trust me, I went crazy trying to watch the film over and over again just to try and hear it but it's not there.

Update 2:

Wow guys ur a really big help....NOT! what is up with you people!?

Answer 1

Favorite Answer

Oh they're in there, you just can't hear them above the screaming. ;-P

Answer 2

Simple, sometimes it is subliminal. Your conscious self is not hearing a thing but somewhere in your subconscious, things take place themselves. That's why sometimes you get the scare of nightmares because of what you did not "see" and "hear".

Answer 3

because the music is no count in horror movies

Answer 4

because they are from horror movies