I spent a college summer (in the mid-1980s) working at a piston ring company. It was a multi-union shop, but as a temp, I wasn't required to join (thankfully!)
The machines, as machines do, would often need fixing and adjustment. The most common fix would have taken me about 3 minutes to perform. However, union rules prevented me from fixing it. First, I turned it off (surprisingly, I WAS allowed to do that). Then, the power cord had to be unplugged from the outlet. That required an electrical union person. Then, the hydraulics needed to be disconnected. That required another union person. And the water supply needed to be disconnected, requiring yet a third union person. Finally, the adjustments required a wrench and a fourth union person to turn it. Then, put it all back together required finding all the right union people again. And god forbid one of the unions was on break.
What I could have easily done by myself in 3 minutes required 4 people and anywhere from 30-90 minutes. Not because of real training or safety needs, just because of union rules formulated to keep otherwise unneeded people employed.
Now multiply this by a half-dozen machines requiring this type of work 1-2 times per week (possibly per shift, too).
Brian Bronson