In a message dated 97-07-09 00:54:41 EDT, you write:
<< I refer to movies that do NOT have scenes that the trailers DO. >>
Trailers are ADVERTISEMENTS for the films they portray. While they generally
contain footage from the film, there is certainly no LEGAL or MORAL
requirement that they do so exclusively. The idea is to get you - the
audience - to want to go see it by teasing the subject.
On a practical matter, as you mentioned, the trailers are screened while the
film is often still in post. For example, trailers almost never have any
music in them that is-from/will-be in the final cut.
Screen-L is sponsored by the Telecommunication & Film Dept., the
University of Alabama.