Earlier quoted context omitted.
"Why would colleges want to hire tenure-track professors if adjuncts can teach the same number of students for less money?" That is precisely the point. There is an oversupply of people willing to do the job and thus people are willing to do it for less money (teaching adjunct). If there were a shortage, then the university would be forced to pay more and give more benefits (hire tenure track).
There seems to be a lot of confusion in this thread about what one another is saying. sparsevector said that colleges are not oversupplied, because there's a lot of demand for them. wtvanhest replied with a comment that sounds as if colleges are oversupplied, when in fact his evidence suggests that teachers are oversupplied. That's off-topic. So I was trying to point that out, and now you're repeating wtvanhest's arg…
I am talking about professors since that is what the article is about and completely not worrying about colleges since that is off topic.
The entire point of the article is that a person who decides to get a PhD in history should be paid because they went to school for 4 years. To me, that concept is ridiculous and people don't get to be paid a lot for what they want to do in the absence of basic economic theory.
Too many professors, not enough demand = low pay. It sucks that person made that choice, but there are plenty of secretarial jobs which pay above poverty level which someone with a PhD in history could get.