Oh I'm sure there's still some people who assume that "everyone" speaks french, but in the 1930s (or 1850s) that assumption was more reasonable and thus more common. (If classist, I'm pretty sure the majority of everyday people didn't know french. I think. Maybe?)

You're right, now that I think of it the odd times I've encountered untranslated german in books or movies I've at best been able to get the vague gist of what was being said. *remembers the Dr Who episode with the Daleks going "Exterminieren! Exterminieren!" which isn't even a real german word*