The transient time builders are not going to waste time and energy on a union, they'll be afraid it will slow their upgrade... that has to come from senior lifers, and mid-grade possible lifers. The senior lifers are too well taken care of, even today. Also many of them have ranches, farms, businesses, even full-time jobs... they can have a normal life plus make an extra $150K flying standups 3-4 nights/week. In the west. Low motivation to rock that boat. A few folks like MM are exceptions... but when he punched, I saw the writing.
Remember most of the alpa chest thumpers from the eastern regionals did not earn a union, they inherited it from old-skool prop trash. And anybody from XJT has an ulterior motive... they want an SLI. Bad.