Stress
The job satisfaction rate for millwrights is really high (source). This is the type of job that only attracts a certain type of person, so it's rare to find someone in the field who doesn't want to be there. When everybody around you loves their job, it's like a big ol' party—if parties had lots of power tools and uber-responsible safety standards.
You see a mechanical problem, you fix it. End of story. No annoying office small talk about Mondays, no email chains, no report deadlines—just you and your tools, fixing a machine. It's almost like a beach vacation.