I thought it was weird when people were talking to themselves with bluetooth
When Bluetooth headsets became small enough to be inconspicuous I lived in a marginal neighborhood. When my wife and I would go out, we'd play a guessing game called "Bluetooth or mental illness."
I play a game with people talking on their BT device, where I pretend I don't already know that, and I talk back to them as if they're talking to me. The object of the game is to see how long I can keep them from their other conversation by refusing to acknowledge their device.
When Bluetooth headsets became small enough to be inconspicuous I lived in a marginal neighborhood. When my wife and I would go out, we'd play a guessing game called "Bluetooth or mental illness."