My dad, a musician, belonged to a union for at least two decades. When he became a parent and took on the dreaded Day Job, his trombone-related activities became a weekend thing. His income from gigs wasn't enough to justify paying union dues. And so, he entered the shadowy world of independent musicians, playing neighborhood festivals and occasional weddings, which were paid "under the table." Taxes? No idea. Never asked; never thought about it, and now he is not available for inquiry.
Mom was a union member during the few years she worked at a factory. It was an in-house union, apparently, and they were often plagued by the United Auto Workers wanting to take it over. "I wish they'd leave our little union alone," she'd say; it sounded like the UAW was a more oppressive force than the management. I never heard her say anything negative about her employer. I guess she figured, they hired a woman in her 50s who'd been a homemaker for 20 years, so they couldn't be all that bad.