White collar work isn't necessarily guaranteed to never experience a bust, but your skills are mostly pretty portable across industries. HR, accounting, management are similar enough no matter what industry you're in. If you lay glass for office buildings, there isn't much else you can do if people stop building office buildings. You can be doing great one year, then the next your career no longer exists.
Additionally, what the heck do you do if you get hurt? My dad is a retired plumber but pushed me into college because of his constant physical misery from playing sports on top of manual labor. And lo and behold, I had severe spine problems in my mid-30s. Three surgeries in 16 months. Two fusions. I couldn't put my own shoes on for two years. I'd have been done as a skilled trade. But I can easily enough keep typing on a laptop even if I can't walk any more.
what skills are those? Being able to operate excel and outlook? I'm not sure about HR and management, but accounting has very specific rules to follow that you can't just let a random desk jockey do it.
In my experience (highway/heavy industrial construction) both industry and institution is suffering greatly from the loss of more experienced hands without a proper training/mentoring pipeline to bring new folks up to speed. Not only in the glut of middle managers in industry who serve more to obstruct the flow of work than assist it, but also the loss of institutional knowledge embodied by employees with decades of experience. I've seen projects grind to a standstill, or take that much longer to start, as technical questions get bounced around state/federal agencies forever with the general tune of "I don't know anything about that, XXX in dept Y was our guy for that but he retired 9 years ago. I don't want to be responsible for this so let's ask another dept." Each bounce adding weeks to the timeline.
I started working in '07, and got one good summer construction season under my belt before everything crashed and burned. I watched first hand as belt-tightening took its effect across industry, those more junior were shown the door and those with seniority were kept and cherished, or they chose to retire. The effects of this are showing even now, those with seniority who chose to stay then have been retiring since. In union terms there is a big gap in the journeymen level folks between the 20-30+ year guys and the fresh faced apprentices.
Decades of pushing kids towards STEM and collegiate programs while fostering some form of disdain for blue collar work may also play into this, but those are societal questions way outside my realm.