The cast and staff and producers, etc. would doubtlessly be ticked off at not being credited by name at the movie’s end, but is there typically a legal or contractual requirement to credit them?
Contractual. SAG (I believe) has credit requirements all spelled out for all SAG productions.
For the vast majority of the people who work on a film, prolly not a legal or contractual obligation to put them in the credits.
But the big stars and the directors who do have personal contracts will certainly have language about screen credit being given which may include where in the order of things that particular person’s name will appear, how big the type has to be, whether or not each credit is listed individually or lumped in one big credit (i.e. “Director: Alan Smithee” “Producer: Alan Smithee” or just “Produced and Directed by Alan Smithee”), etc.
ETA: And as silenus points out, SAG has their own contractual requirements that detail who gets a credit based on the work they do for the production.
Actors, writers, directors, cinematographers, etc. usually have requirements in their guild agreements.
Caterers, drivers, etc, (i.e., support staff) are usually given credit as a courtesy (and as part of their contract).
There has to have been a thread about this, but I asked a SAG member about the “credit squeezing” that happens on TV so they can show more ads and he said the studios and unions went along with it.
I believe there also used to be SAG guild rules about credits being at the beginning of films but that rule was relaxed or changed starting sometime in the 1970’s.
Famously George Lucas had to pay a fine because he refused to list the credits in the beginning of Star Wars in 1977. He wanted the opening ‘punch’ of the music and title to then be immediately followed by the opening crawl (he was very right to want this). We take this for granted now (Man of Steel didn’t even have an opening title screen).
There’s the Directors Guild of America, the Producers Guild of America, and the Screen Actors Guild. Each requires members to include proper credits in films.
The Directors Guild won the little insiders game, so the director must be the last name shown before the film or the film name shown after the film. Cite. Some other rules.
This SAG pdf also shows complex credit requirements.
And the Producers Guild outdoes both.
TL;DR Here’s a quick overview
Up to 1978, you had to have an actual copyright notice in a movie or TV show. So that was something most everyone threw in as part of the credits. And that was important. (They still do, of course, just to make other things easier.)
Sometimes it was left off something and the film/show entered the public domain. E.g., *Night of the Living Dead’*s title was changed. And since the copyright notice was on the original title slide but not put on the new title slide, it lost copyright protection under the then US law. Some episodes of The Andy Griffith Show also were aired without a copyright notice and were thought for a while to be public domain but apparently aren’t. (Even with the copyrighted theme song replaced.) Nonetheless you still see those on DVDs in the dollar bin. Etc.
He also quit the guild after that bullshit.
And Apocalypse Now did?
On the other hand, what’s the most recent film without closing credits? The latest one I can think of is Monty Python & the Holy Grail. Reportedly, the plan was that, right after the screen went black at the end, there would be another short film that would contain the credits, but they ran out of money before they could do it.
It wasn’t that he had no opening credits for Star Wars. The issue was no director credit opening for Empire Strikes Back while Lucas’s name was in the production company’s name.
Actually, I don’t, and find it a bit annoying. Why? The rule seems to be that they do an opening credits style sequence at some point, then do the closing credits. The MCU films seem to all do this - the end of the first sequence is when they add their little tag sequence (Civil War has Peter Parker explaining to Aunt May that he was in a fight with a guy named Steve from Brooklyn), then you get traditional closing credits.