How long of a time frame you thinking here? I can walk you through the social worth of librarians from the 19th century to now in America, but I can't shake a stick at whatever they were doing in the Great Library of Alexandria!

Can you possibly clarify for what you are discussing? Librarians have been used to manage physical collections of books for hundreds of years and all over the world. As such, their jobs have changed considerably based on time and location. Can you narrow down your question to a country or time period?