Librarians go to school to learn how to manage information, whether it is in book format or otherwise. (We tend to think of libraries as places with books because, for so much of human history, that’s how information was stored.)

They are not supposed to have more information in their heads, they are supposed to know how to find (source) information, catalogue and categorize it, identify good information from bad information, good information sources from bad ones, and teach others how to do so as well.

I had to tell a bunch of librarians that LLMs are literally language models made to mimic language patterns, and are not made to be factually correct. They understood it when I put it that way, but librarians are supposed to be “information professionals”. If they, as a slightly better trained subset of the general public, don’t know that, the general public has no hope of knowing that.