It requires a card from a subscribing library. Not all subscribing libraries are public libraries and not all libraries subscribe. They don’t have exclusive streaming rights to much of their collection, although they often have stuff that no one else will have because their focus tends to be on indie/foreign/documentary films (not exclusively, but largely).

I live in Chicago and signed up to the Chicago Public Library last year for a "virtual library card" and they didn't do anything to authenticate my location or existence. Just throwing that out there...