Kids used to have to be taught how to use the library. Card catalogue, Dewey decimal system, all that. The kinds of things one may find at a library other than books. People aren't born knowing this stuff and may not realize what can and cannot be gained from a resource, or how to go about getting it, if they aren't told at some point.

Hell, you have to teach kids about book features like captions and tables of contents and indices and footnotes and, believe it or not, kids aren't always great at picking up that knowledge even when taught.