I have seen other people's trails on rental cars and I've always wondered why would they connect their phones to basically what is an unknown system, exposed to

I have seen other people's trails on rental cars and I've always wondered why would they connect their phones to basically what is an unknown system, exposed to just about anyone. Maybe I'm just weird. Never had any reason to connect my phone to the car, not rental nor my own. I make phonecalls from my... well, phone, not the car. I use my phone's Google Maps if I need to refresh my memory to get driving instructions. I don't have music on my phone either. It seems that being a bit ignorant to new technology does pay off at times.