In these parts of the world (Romania, Eastern-Europe, granted, a very Francophile country back in the day) middle-class people were regularly using French as the means of personal communication in the inter-war period. Just recently I’ve seen a post-card sent by a Romanian husband to his Romanian wife from a Romanian seaside resort sometime around 1930 which was written entirely in French. Lots of first names were also being French-ified for written informal communication, like the Romanian Gheorghe being changed into the French Georges. Once the communists came to power after WW2 almost all of that vanished, partly because the newly arisen middle-classes were not as “cultured” as the inter-war middle-class (even though knowing French was still seen as you being “an intellectual”, so to speak).

Once the communists fell and capitalism took over English sort of became lingua-franca for business communication, but you’d be hard-pressed to find any people using it for personal communication the same as they were using French before WW2. Not trying to refute your observation or anything, which I find entirely correct, just wanted to add a small piece of language trivia.