Didn't notice before since I was always inside the car, but I noticed the volume is a bit loud from the outside and decided to do something testing. This is a big privacy concern if you don't want people listening to your calls.

Anyway, if you have a smart stereo where you can connect your phone and it plays through the speakers, try it out:
Have someone inside the car, that's connected to the stereo, call you while you're standing outside.

Even with all the doors and windows closed, I could hear myself amplified through the car speakers from the outside. It seems like I can hear the calls clearer outside than inside, which is crazy since there aren't any outward facing speakers... are there?
I'm using a Sony XAV-AX1000 unit connected to Apple Carplay.