Sound is an abstract energy. In movies what matters is how you manipulate it to get the intended reaction from the audience. It is not about putting some sounds matching the visuals. But it is necessary to understand what audience will feel after hearing the sound or silence. For that we recreate the sound. For example we do foley recording. It means we recreate a sound in the studio recording. A camp fire sound can be made out of plastic crackles. It does not mean that natural sound is not used in movies. Recording natural sound is called ambience recording. But it is also edited and manipulated in the studio environment according to the psychological requirement. It is all about feelings - not about being realistic.
