You said you just have a Bluetooth audio connection - so you’re just listening to the readout of the directions? That doesn’t sound like a great experience.

The phone has a screen and sits on the dash. I don't use BT audio for directions, only for calls and Apple Music.

> The phone has a screen and sits on the dash.

It doesn’t take a leap of imagination to understand why a proper large screen, integration into the instrument cluster, and the HUD if you have one, is safer and easier to use than a tiny phone hanging off your dash.

You’re also for example missing out on your car's ability to do dead reckoning when there is a poor GPS signal.

Depends how badly designed your car is. Mine sits just to the top left of the steering wheel.

The phone does dead reckoning as well. It has accelerometers and a compass built in.