maybe in CS, but if you have a PhD in a STEM field, you're not going to be looking at a wasteland in private industry for jobs that demand a PhD. Good luck getting a job running a big firm's private research lab without a PhD, and tens of thousands of companies demand that PhD. Chemistry PhD? what company doesn't need one of them, if not dozens. Materials science? yeah, you are going to be finding lots of companies that want their product development team run by someone holding a PhD at least. BioTech and Pharma aren't being run by people who just have a bachelor's, and there are over 10,000 private pharmaceutical research labs. Even your Wonder Bread has more than one food science PhD behind the scenes working on it. Any random big agribusiness alone is going to expect you have a PhD in crop science to conduct trials for pesticide development, and they're going to want a chemistry PhD to help develop the formulation, and an entomology PhD to investigate the effect their product has on insect biology, a soil science PhD to study the effect on soil, biochem PhD, biotech PhD, all sorts of engineering PhDs, probably some statistics/math PhDs...

Now, if your PhD is in the humanities, you're not looking at the same situation. It's almost bizarre they call the degree the same name, since a PhD in the humanities takes you on a completely different path. I don't think many companies are demanding a History or English or German literature PhD. Sometimes this can make you a competitive candidate for a job in a completely unrelated field, but those jobs have no need for a PhD, it's just something that makes you stand out when 100 overqualified people are applying for the same job. So will a candidate working in the Peace Corps. Or volunteering hundreds of hours a year. Those getting a history PhD are competing for the...what, 60? 90? jobs in the entire nation that require a history PhD, which is being a professor that gives other people history PhDs. So of course, you will only get such a job if you go to a top 10 school, and the chances of this are basically less than becoming a professional athlete. So the vast disparity between a humanities PhD which has no sustainable aspirational track, vs. a STEM PhD where you become a qualified candidate for both academia/the government which hires many PhDs, and industry, which also has a demand for PhD-trained candidates. Probably 3/4 of STEM PhDs don't work for a school or the government.