How about this one...
How many times have you been in a tour group and someone who speaks a foreign language is right next to you talking to someone in their own group in their loudest voice?
it is like they think you can't hear them if they aren't speaking English.
I admit we have done this myself to other tour groups speaking other languages. My wife was on the other side yelling at me like they were just a machine making noise to talk over, and I answered the same way (and got a lot of dirty looks). It's too easy to forget they are people trying to listen when you don't understand what they are saying.