Do you think they would join if they weren't forced to join? If so why should they be forced to join? This kind of arrangement is illegal in Europe so it isn't required to get high union participation.
I’m going to be a bit handwavy here:
generally - crew members do not work for a specific company, so the problem of a “Union only” job is perhaps somewhat different. Crew members are all functionally contractors for that one specific production. There are no long term contractual obligations. After that production is over, they have to hunt around for their next gig which reinforces the relationship based job economy of Hollywood labor.
When a production is kicking, off department heads will be hired (for instance, a Director is Photography) and they will hire the crew members below them in the hierarchy. Many department heads will have their regular group of people they call, and it can be difficult to break into the network. Most people who join a union have experience, training, references, etc which help build those connections.
Again, non-union film production happens all the time. The benefits of joining one of the unions are positive enough that most people do, but You don’t have to be in Local 600 to shoot a movie.
This is only required in some cases. In a “union shoot” as it were. These are rare in comparison to non-union films. Every actor has many examples of non-union films they participate in.
Usually big stars work in non-union roles and films to give younger professionals an opportunity. The star provides marketing power for a smaller Non-union production. Then people can join the union as well.
Actors aren't allowed to participate in non-union films. They sometimes do anyway but the contract says they can't.
> SAG-AFTRA members cannot accept an acting role in any studio, independent, low-budget, pilot, experimental, non-profit, interactive, educational, student, or ANY production, unless that producer has signed a Contract or Letter of Agreement with SAG-AFTRA.
> Members who are found in violation of these rules are subject to serious fines and discipline by a panel of union peers.
https://www.sagaftra.org/what-happens-if-i-accept-non-union-...
To your question, I was a member of IATSE Local 600 (Cinematographer’s Guild) as a loader, 2nd AC, digital utility and sometimes focus puller. I noted my union affiliation upthread. Members are explicitly allowed to work on non-union jobs, but there is an expectation that you call it in if the budget is over ~1 million. Below that, the union is not particularly interested in attempting to flip the show so no one cares.
(This is where I would call you out for your tone of ignorant self superiority, but I’ll just defer to the HN guidelines and let it drop)