It is natural that students and postdocs should come to faculty members to get career advice. Should I do a Ph.D? Should I do a postdoc? Should I leave academia?
Some faculty give excellent and balanced advice. Particularly, they give students a realistic picture of the [low] chances of a Ph.D (and postdoc) leading to an academic career, particularly at a leading university in the Western world. A good place to start the discussion is the data here. A related statistic to consider is that of the local department. What is the ratio of the Ph.D graduation rate to the faculty hiring rate? For example, in the School of Mathematics and Physics at UQ we currently have close to 100 enrolled Ph.D students. That means we graduate about 20-25 per year. We probably hire faculty at roughly the rate of 0-4 per year.
Unfortunately, some faculty don't exactly go out of their way to inform students and postdocs of these painful realities and/or they give the impression, either directly or subtly, that jobs outside academia are somehow second-rate.
However, I think there may be an additional subtle underlying psychological problem. This exists even when faculty give realistic and sober advice. The mere existence of a faculty member gives the message, particularly to wishful thinkers:
"I made it. I beat the odds. So you can you."