I fairly regularly need older/more obscure stuff that I can't immediately get through the libraries I have access to. This is especially frustrating when a digital version exists but is paywalled.
Librarians are obviously amazing, but all the time and effort of interlibrary loan requests can be avoided when I can just borrow the book I need from the internet archive for an hour and get exactly what I need without me or anyone else even having to leave the room.