I got my physics PhD in 1993. By this time, this expectation was already held in disregard. Most students were aware of what we called the "birth control problem." My dad got his PhD in the 1950s, and told me that it was common knowledge back then too.
But while students vaguely knew that most of us would not end up on this path, we got little or no guidance on what else we could do. A common aspiration was to teach at a lower tier school, but the academic job market was saturated from top to bottom. I was ready to go into some kind of engineering. A lot of us became programmers.
I got lucky -- a friend of a friend owned a company, and hired me.
My experience is that the understanding of the problem is apparent to post-graduates and older, as well as a number of people outside of academia. Among my undergraduate class and my entering first-year graduate class, understanding of that reality -- that many of them (which, probabilistically meant you) would not become professors -- was limited at best.
That's fair. It may be something that students have been told but don't really internalize. Everybody at the tournament wants to believe that they stand a chance. I know this is true of students in the humanities too. Everybody is actively putting off facing the reality.
One thing I do remember is that as undergrads, we were advised to maintain a pretense of wanting to pursue an academic career, even if we had other plans. If you told them that you intended to finish with a masters and go into industry, you would probably not get accepted, would not get funding, and would be treated as a second class citizen. So students were pretty much told to inflate their expectations. That was a long time ago, and I don't know how it is now.
I didn't become a good enough research scientist to compete for a trophy gig in academia. What I saw is that my own university was hiring up, i.e., only considering applicants from higher ranked schools. That meant my chances were somewhere close to zero. I got to know the post-docs and understood their grind. But also, I became more interested in gadgets and making things work, than in directing fundamental research.
But while students vaguely knew that most of us would not end up on this path, we got little or no guidance on what else we could do. A common aspiration was to teach at a lower tier school, but the academic job market was saturated from top to bottom. I was ready to go into some kind of engineering. A lot of us became programmers.
I got lucky -- a friend of a friend owned a company, and hired me.