A lot of jobs are easy on a day-to-day basis, but get hard every once in a while when some edge case comes up and you’ve gotta have a breadth of background knowledge of the field to handle it effectively. It’s why AI seems so useful to middle managers who don’t realize that edge cases exist; their employees can handle them without issue, but AI spits out total garbage and calls it done. I’d imagine librarians are indeed dealing with people looking for the latest fad book more often than not, but they still have to be prepared for the person coming in wanting to know all about insect phylogeny.