Here is an explanation from 1994 by Dr. David Goodstein of Caltech, who testified to Congress on this back then, whose "The Big Crunch" essay concludes: https://www.its.caltech.edu/~dg/crunch_art.html
"Let me finish by summarizing what I've been trying to tell you. We stand at an historic juncture in the history of science. The long era of exponential expansion ended decades ago, but we have not yet reconciled ourselves to that fact. The present social structure of science, by which I mean institutions, education, funding, publications and so on all evolved during the period of exponential expansion, before The Big Crunch. They are not suited to the unknown future we face. Today's scientific leaders, in the universities, government, industry and the scientific societies are mostly people who came of age during the golden era, 1950 - 1970. I am myself part of that generation. We think those were normal times and expect them to return. But we are wrong. Nothing like it will ever happen again. It is by no means certain that science will even survive, much less flourish, in the difficult times we face. Before it can survive, those of us who have gained so much from the era of scientific elites and scientific illiterates must learn to face reality, and admit that those days are gone forever."

And see also "Disciplined Minds" from 2000 about some other consequences: http://disciplinedminds.tripod.com/ "In this riveting book about the world of professional work, Jeff Schmidt demonstrates that the workplace is a battleground for the very identity of the individual, as is graduate school, where professionals are trained. He shows that professional work is inherently political, and that professionals are hired to subordinate their own vision and maintain strict "ideological discipline." The hidden root of much career dissatisfaction, argues Schmidt, is the professional's lack of control over the political component of his or her creative work. Many professionals set out to make a contribution to society and add meaning to their lives. Yet our system of professional education and employment abusively inculcates an acceptance of politically subordinate roles in which professionals typically do not make a significant difference, undermining the creative potential of individuals, organizations and even democracy. Schmidt details the battle one must fight to be an independent thinker and to pursue one's own social vision in today's corporate society."

Or Philip Greenspun from 2006: http://philip.greenspun.com/careers/women-in-science
"This is how things are likely to go for the smartest kid you sat next to in college. He got into Stanford for graduate school. He got a postdoc at MIT. His experiment worked out and he was therefore fortunate to land a job at University of California, Irvine. But at the end of the day, his research wasn't quite interesting or topical enough that the university wanted to commit to paying him a salary for the rest of his life. He is now 44 years old, with a family to feed, and looking for job with a "second rate has-been" label on his forehead. Why then, does anyone think that science is a sufficiently good career that people should debate who is privileged enough to work at it? Sample bias."

Or the Village Voice from 2004 about how it is even worse in the humanities than sci/tech grad school:
https://web.archive.org/web/20130115173649/http://www.villag...
"Here's an exciting career opportunity you won't see in the classified ads. For the first six to 10 years, it pays less than $20,000 and demands superhuman levels of commitment in a Dickensian environment. Forget about marriage, a mortgage, or even Thanksgiving dinners, as the focus of your entire life narrows to the production, to exacting specifications, of a 300-page document less than a dozen people will read. Then it's time for advancement: Apply to 50 far-flung, undesirable locations, with a 30 to 40 percent chance of being offered any position at all. You may end up living 100 miles from your spouse and commuting to three different work locations a week. You may end up $50,000 in debt, with no health insurance, feeding your kids with food stamps. If you are the luckiest out of every five entrants, you may win the profession's ultimate prize: A comfortable middle-class job, for the rest of your life, with summers off. Welcome to the world of the humanities Ph.D. student, 2004, where promises mean little and revolt is in the air."

The odd of success are probably even lower now with expanding use of adjuncts to replace tenured faculty.

Of course, the irony is that US society now has more than enough wealth so that anyone who wanted to could live like a graduate student researching whatever they wanted on a basic income.