@rojo—Low level clerks mostly do the work you describe.
LIbrarians are trained to catalog original materials (stuff like local archives or school yearbooks—stuff not found online) Cataloging is actually a pretty complex process with a lot of different philosophies of order. You can even get your PhD just in cataloging.
Collection Development—Librarians learn how to select the best materials for their department or library. This includes writing an official collection development policy and growing your collection to be useful to your population. You can’t just randomly buy stuff. Collection development is also important for de-selecting materials (throwing out old books that no longer fit the needs of the population)
Program Development—This is mainly for public libraries, but you learn how to run events and evaluate them so you can improve them in the future. I was a programmer in a public librarian for years.
They also have library management training, archival restoration and book maintenance. There are special libraries where you learn to catalog and collect maps, theater equipment and all kinds of odd stuff. You also take
There’s more. This is just off the top of my head. Thinking that a librarian just shelves books is like thinking the minister at church only works on Sunday morning.
Just a word of advice: Do NOT ask why librarians need special degrees on your job interview. This is something that annoys and insults most librarians.