Well, it depends. In the tv shows Lost and Heroes, both of which are ensemble shows where some of the characters aren't English native speakers, you get subtitled conversations, and that very much works for me. But those are present day stories, and the command of English (or lack of same) quite often is a plot point, as is the American characters not understanding the Korean ones to the same degree the audience does in Lost. In historical movies, I'd say that as you point out, it's a given that in a scene where Rommel talks to his aide he talks in German, etc.