Unfortunately the US Academia produces a glut of PhDs, with absolutely no regard for the professional or career prospects of those PhDs. The latest figures put the number of newly minted PhDs in the US at 58,000. Arguably the only jobs where PhD level skills are directly relevant are those in Academia itself, but those jobs have been becoming increasingly hard to get. The latest estimate is that there are only about 10,000 – 12,000 tenure track job openings in the US each year. Some fraction of the surplus is captured by the postdoc market, but not enough to make the whole system sustainable.
PhD education is primarily subsidized from two sources of funding – grants from the government and the paltry teaching stipends that most PhDs have to resort to. There are ethical problems with both of them. The government funding is, obviously, downstream from taxes. So we are asking the public to pay for (costly) skill acquisition that in most cases have absolutely no practical value. The response to this argument is that the value of (PhD) research is that it expands human knowledge. OK, maybe. But the fact is that 80-98% of all PhD theses are never cited. IMHO, the problem is even worse than that. There is a very powerful publishing-citation cartel in place that operates through you-cite-my-student-I-cite-yours mechanisms. So in other words, it is highly unlikely that the PhD system we have right now in place is even close to being the optimal system for creating new insights and knowledge.
Another challenge to the skeptical view of the value of PhD is that those programs help create objective, rigorous thinkers, something that is valuable across the board in our society. This is a variation on the “transfer learning” theory of the value of education, which, I am sorry to say, has not been verified through any kind of actual empirical study. A few attempts to validate it have been, at best, inconclusive. And anyone who has sat through a single faculty meeting would find the notion that these people are “objective, rigorous thinkers” laughable.