- Legal/contractual obligations to list all staff who've worked on film
- Evidence that staff have worked on film, which can be used to help them gain future employment
- Some movie-goers are extremely interested in credits and finding out who was responsible for what
E! Online were asked a question about why movie credit were so long and as part of their answer stated:
"Films have always employed dozens (if not hundreds) of people in
various jobs," Clark University director of screen studies Tim Shary
tells this B!tch. "But before the '60s, they tended to be in teams,
and usually only the leader of the unit received onscreen credit. So,
the art director would be listed but not all of the people (painters,
decorators, landscapers, carpenters, etc.) that worked for him or her.
"Now, almost everyone who works on a film is a member of a union, and
they have expectations about getting onscreen credit."
Could a director like Spielberg or a producer like Scott Rudin decide
to eliminate those credits during one of his 18 daily ego meltdowns?
Not likely, I'm told. During film's golden age, most movie workers
were under contract to a studio, so the suits could credit their
drones--or not--as they saw fit. Today, people hire themselves out
film by film, giving them and their unions more power.
"The presence of many credits today are adjudicated by unions and
guilds," says Penn State senior film lecturer Kevin J. Hagopian. "So,
Steven Spielberg, even as a producer, could not decide simply to leave
off these names."
...One other factor: cheaper movies. Black-turtlenecked indie fans
love to joke that the size of a small film's credits is inversely
proportional to the size of its budget. (What, you expected these
people to have a real sense of humor?) Instead of paying cash,
indie-film producers often offer key spaces in their credits as a
"When freelancing replaced the studio contract system, studios and
producers realized they could pay people less if they gave them
credit," San Francisco State University film professor Joseph McBride
says. "So, the proliferation of credits went bananas in the '70s and
'80s, to the point that now even the honey-wagon driver is credited."
So there does appear to be legalities involved in having people gain credits. Some examples of this can be seen for particular "groups":
- Writer's Guild
- Producer's Guild
Acknowledgement used as a form of intellectual property
Quoting directly from Wikipedia, which rather nicely sums it up:
In the creative arts and scientific literature, an acknowledgment
(also spelled acknowledgement) is an expression of gratitude for
assistance in creating an original work.
Receiving credit by way of
acknowledgment rather than authorship indicates that the person or
organization did not have a direct hand in producing the work in
question, but may have contributed funding, criticism, or
encouragement to the author(s). Various schemes exist for classifying
acknowledgments; Cronin et al.give the following six categories:
a) moral support
b) financial support
c) editorial support
e) instrumental/technical support
f) conceptual support, or peer
interactive communication (PIC)
Apart from citation, which is not
usually considered to be an acknowledgment, acknowledgment of
conceptual support is widely considered to be the most important for
identifying intellectual debt. Some acknowledgments of financial
support, on the other hand, may simply be legal formalities imposed by
the granting institution.
So it appears many people, from actors through to cameramen, can use the fact they are included in credits as a form of "proof" on their CV so to speak, to absolutely guarantee they were involved in a project in that particular role.
An example of this on a minor stage, is the IMDB Credit System, which explicitly states that anyone can add their name as an actor to a film, but their system will check it against the official "credits" and remove it if not featured.
Whilst I imagine the majority of film watchers do not watch the end credits, there are a some who do (call them Dawsons) and are genuinely interested in how a particular part of a film was achieved (e.g. how a sound effect was completed or who was in charge of animal safety, etc).
To add in some of the fantastic points made in the comments:
Tom: People want acknowledgement for their hard work with a place in the credits, regardless of whether the audience will watch it.
Damon: The credits add to the length of the movie which increases the amount of money it can be licensed to broadcasters for.
Claudio Miklos: The credits are a piece of film history, recording for all time exactly who did what with a film.