Let’s say you’re an actor. Not an A-lister like Tom Hanks or Jack Nicholson, but a commercial actor. You manage to get cast in a few commercials per year. And you get paid every time a commercial airs (overly simplified, but there’s a minimum and then more for additional runs).
Because you’re on a national spot for Taco Bell, there’s no way Bell Taco will also hire you for their spot. Neither, most likely, will any other non-related chain (Circuit City, Pampers, etc) because they don’t want overexposure. They want their ad to stand out, not the actor who is suddenly appearing all over the place. So those 4-5 gigs/year have to pay enough that you can survive.
How about film writers, then? You write a movie, you get lucky enough to sell it, you get a paycheck. While the movie is in production, you’re probably on set making changes and updating dialogue, etc. You get paid for that, just like the grips, gaffers, wardrobe, etc.
Now the movie ends. The grips, gaffers, wardrobe, etc, all go straight to another job.
As a writer, you now have to spend 6-12 months writing another script. And no one is giving you a dime (unless you are lucky enough to get HIRED to write another script).
That’s another reason they get residuals and the rest of the crew doesn’t.
Also, there’s a bigger issue: a writer creates a piece. So does a director. So does a producer. Gaffers and grips don’t. They are talented individuals, but are essentially blue collar skilled craftsmen. Really good carpenters and riggers. They have a union, they get benefits, but they are not the creative forces that make a project come to life – they are the soldiers that do what the generals tell them to do. Why SHOULD they get residuals?
Do you go to movies just because your favorite director/actor/producer made it? Many people do. Who the heck goes because their favorite grip worked on a show? Just the grip’s friends and family, that’s who.
The idea behind residuals is that the creative forces that make a project actually happen deserve a cut of the profits, just as much as the financial forces that make a project happen do (even if it’s a smaller cut). No way does that apply to a production assistant who runs around and gets coffee. They don’t deserve continuing pay for that kind of work, I’m sorry.
So that’s a partial set of reasons that some jobs get residuals and others don’t.
PS – the one group that doesn’t get them that should is editors. Very involved creatively, make a huge difference to a project, but have one of the weakest unions around.