Earlier quoted context omitted.
Not for the creative roles. Maybe you're thinking of guilds? They're both forms of collective representation, but quite different on the ground.
They certainly are a union and describe themselves as such. For example, from https://www.wga.org/the-guild/about-us/guide-to-the-guild "We are the Writers Guild of America West (WGAW), a labor union composed of the thousands of writers who write the content for television shows, movies, news programs, documentaries, animation, and Internet and mobile phones (new media) that keep audiences constantly entertained and…
If you are a television producer hiring a writer, you don't go to the WGA. You just interview a bunch of writers, select the one you want, and offer them the job. Like you would any other job, really, except that if the writer is a member of the guild then the terms of employment must meet some certain standards, with rules about crediting and overtime, etc. But so long as you adhere to the guild's rules, it's like hiring any other independent contractor.
But if you're a ship captain wanting to offload cargo, you go to the longshoreman's union and as for N day workers. You don't pick who, and you don't negotiate rates other than specifying (and paying for) the desired experience level. You ask for N longshoremen, and you get N warm bodies and the bill.
To the point of this conversation, a guild makes more sense in a creative project where the skill and art of the worker matters to the end result. If you're producing a TV comedy, you really need to make sure you employ the correct writers. Likewise for game designers.