It's All Greek to Me

I have been bilingual my entire life. In fact, my first language was Greek, and one of the first things I remember my parents telling me is that we should never speak to one another in our native language if there are people around us who do not understand it. That's why I am continually amazed that people who are bilingual, and who should know better, often overlook this social cue. I suppose that it flatters them in some way, makes them feel better about themselves.