Almost by definition, if you're doing a Postdoc in a STEM field, you're probably qualified for a relatively well-paying job in industry [1].
And it's not like universities don't know this, people have been complaining about it for forever. They know if they were to just hire a person with a relevant PhD to do work, they'd ask for a good wage, so instead they dangle this "maybe you'll qualify for a tenured professor job eventually if you do underpaid labor for us for N years..."
------
My relationship with academia is...complicated. I dropped out of college in 2012, worked as an engineer for awhile, did a brief stint as a researchey-person at NYU, got laid-off from there, worked in industry for another several years, tried school again in 2018 and dropped out again in 2019, finally finished my degree in 2021, and started a PhD in 2022, and did an adjunct lecturer thing from second-half of 2022 to first-half 2023.
Since I was working full time (and couldn't pay my mortgage on academic wages), I was doing a PhD at University of York part-time remotely. It was fun, but I wasn't just paid poorly, I had to pay them! About $15,000-$16,000/year American [2]! Even though I was doing work for the school, writing code for them that's not categorically different than the code I got paid yuppie engineer salary for, I was losing money in this prospect (and not just the normal opportunity cost kind).
I did it for two years, but I dropped it in November of last year because it was an expensive thing that I wasn't convinced was actually going to pay off for me. The PhD was already pretty self-guided, I could still research the topics I was interested in for free, academia's pace is glacial-at-best, and I didn't burn any bridges so I could go back later if I really wanted.
I might still publish a paper with my advisor in this next year (that's still pending), but of course since I'm not enrolled-in and paying-money-to the school, it won't count towards any credential. I think I'm ok with that.
[1] There might be exception to this but I can't think of many.
[2] depending on the dollar->pound exchange rate.