In my youth I spent a lot of time in libraries and to my recollection, there were various staff roles. There's a lot of labor involved in running a library and most of it was done by clerks and pages. Actual librarians were somewhat scarce and they weren't just shelving books, a lot of their responsibilities were pretty high level, such as assisting patrons with research, designing the library's various educational programs, and curating collections of significant works.
I can see how automation features like self checkout could replace some of the pages and clerks, but not the librarians. If for instance a journalist or historian (or anyone as it's a public service!) is doing research for their work, and needs to access the microfilms of old documents, the librarian is there to assist, and their function is invaluable - their existence is an investment by our society in increasing the accessibility and accuracy of facts. It seems like we need more people performing that function in the modern day, not less.
I can see how automation features like self checkout could replace some of the pages and clerks, but not the librarians. If for instance a journalist or historian (or anyone as it's a public service!) is doing research for their work, and needs to access the microfilms of old documents, the librarian is there to assist, and their function is invaluable - their existence is an investment by our society in increasing the accessibility and accuracy of facts. It seems like we need more people performing that function in the modern day, not less.