I don't know that it's so much disdain for blue collar work as what you described right here: the work is unstable. My uncle, both cousins, and brother-in-law are all glaziers. The uncle and cousins have been trying to run a family business for decades and it's boom and bust over and over. My brother-in-law has stuck with the unions and he was making 90k a year when I was still in college, things were great. Then 2008 happened and he was almost completely unemployed for two years and got addicted to heroin and went to prison briefly. He was doing okay again recently with more construction booms in Southern California, but with the shift to work from home and possible death of commercial office buildings, how much longer will that last?

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.