Yes, the library analogy helps explain a lot.

For example, shrinking or expanding the book shelves to accommodate the current number of books would not only be a lot of work for the librarian but also a lot of blockage for patrons trying to browse the library.

Likewise, sorting the books in natural order (by author name for example) creates blockage for the browsing patrons whenever the librarian has to shuffle books around to make room for 100 copies of a best seller by the same author or whenever random books are inserted by patrons out of order (a phenomenon which does happen in real world libraries).

Indexing books by slot number would require the librarian to update the card catalog every time a book is moved, so it's more efficient to index books by author name and/or ISBN.