I would assume (and hope) that a company of that scale is using something like Glacier to hold rarely accessed data, so that storage fees aren't incurred on having it in a hot cache.
Netflix could not use Glacier for rarely accessed films, unless they wanted to impose a watching schedule on their users (i.e. "Bananas is only available on weekends", or similar, and even then, that'd impose even higher fees to move things out of Glacier and onto some other kind of storage). Glacier takes minutes to hours to retrieve files (I'm guessing hours in the case or large movie files). Just because it is "rarely accessed", doesn't mean it doesn't need to be available quickly when it is accessed. And, Glacier is priced for data that is moved in and almost never moved out to other types of storage.
