> Indeed, if the purpose of a PhD is to expand the totality of human knowledge, why was it expected that I would publish 3-4 conference papers to graduate?
This is a question that bothers me quite a bit with respect to EECS (electrical engineering and computer science). In mathematics, one's PhD thesis can often serve as one's first paper (once revised). Funnily enough, the same was true for EECS even at the top tier places in the 1980's - I know of a case at Caltech where the student did not have any publications prior to graduation, and yet went on to become a successful professor.
Is it really true that humanity is producing more knowledge in EECS today per student than it was in the 1980's? I seriously doubt this. In my experience, instead what has happened is that the average "delta" in a conference proceeding has gone down significantly, in spite of the vast increase of words like "novel" and "new" being used, and the ballooning of the average paper length.
In mathematics on the other hand, top quality authors freely admit that a lot of their work can be "implicitly" traced back to the "big names" of the past; indeed this has to be done for conceptual and historical clarity.
I see that you mention Peter Sarnak in your top comment. Peter Sarnak has a a wonderful article at the very end of "The Princeton Companion to Mathematics" on his advice for students. Among other things, he stresses the importance of the "history of ideas", and how it often brings clarity to an entire field.