They are very much as a whole not negligible. They can be--people can get checks for cents sometimes. But they wouldn't go on strike and sign a deal if it never amounted to anything. I'm not even in the industry and have a passing familiarity with the concept; I've just been reading about it and listening to people from it for years.

DGA also has residuals in their contract. IATSE might for some roles, but you can't feasibly give everyone involved in a production residuals. The point of residuals is to hold over people in roles that are very fickle and can go years between jobs, like everyday working actors and writers. If you're going years between jobs getting hired for craft services, your food might just suck.

It would be great if everyone could get a share, but that's not realistic. Big productions can have thousands of people who work on them. Having to send the carpenter on a film a check for two cents yearly would create insane administrative overhead. There has to be a line somewhere.