I'll use the Bluetooth speaker in my car if a family member or friend calls me. Otherwise, I wait until I can make a handheld call. If there is someone else in the car with me, I'll let the caller know. I have a friend who once forgot to mention that her daughter was in the car with her, and I brought up a subject that really should have been kept between us. I asked her to please give me a heads up if that ever happened again.
And I really don't understand why the car speaker is so loud when someone is on a call. I can never hear music clearly from another call, but I can easily hear phone conversations. Does anyone know why that is?