PhD students generally just love research. We sign up for this because it's what we enjoy doing. Companies try hard to recruit us away, but we stay in spite of that, because why would we want to do anything other than work on the one problem we've always wanted to solve?
Maybe it's different in the humanities, but every STEM PhD student I've ever met has low expectations, with the exception of one-- and she has a first authorship on a Nature paper and is working on a Science submission, so I still think she's pretty well-grounded.
Honestly, at this point, finding out that the job market is grim takes only a shred of research, and absolutely the kind of research you should do before applying.
I don't know exactly what I'm going to do when I'm done.
Granted, not everyone thinks like me. But certainly not everyone thinks as you do.
Anecdotal rebuttal: The first conversation I had with my research advisor concerned the difficulty of getting a tenure track position at a research university straight out of Ph. D. school. In her words, "that sort of thing just doesn't really happen anymore in this field (Computer Science)."
There are no delusions of academic grandeur, at least in my neck of the woods. I agree that the Ph.D. may be pursued as a career maneuver, but if your end game is a teaching position at a research university your approach to the program has to be very different (and extremely more ambitious) than someone pursuing industry or other goals. And if you're pursuing a prestigious academic position, you are quickly educated on the slim possibility of attaining it, even if you're willing to post doc.
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The Ph.D. program, in our times at least, is pitched as a quid pro quo: you produce some original research, something worthwhile and of substance, to add to the sum of human knowledge, and in exchange they gain access to an academic career.
The problem is that there are a lot of people paying the quid, and barely anyone getting the quo. Unless you are a student of independent wealth, you are not producing this research out of the goodness of your heart with no greater, more important objective. To the vast, vast majority of people doing their Ph.D's, a Ph.D. is a career maneuver.