If you want audio to start magically playing in the car, and the car is often turned off...
You can't have the phone connect to it. Otherwise it would continually have to poll for a car, which would burn power.
Ergo, you have to have the car initiate the connection, which should happen when the car turns on.
Now, you could either have a "Confirm connect?" every time that happens or you could have it auto-reconnect.
In most circumstances, "Car-initiated, auto-reconnecting Bluetooth" is preferable to the alternatives.
Even if it does have bizarre and annoying UX failure modes.
If you want audio to start magically playing in the car, and the car is often turned off...
You can't have the phone connect to it. Otherwise it would continually have to poll for a car, which would burn power.
Ergo, you have to have the car initiate the connection, which should happen when the car turns on.
Now, you could either have a "Confirm connect?" every time that happens or you could have it auto-reconnect.
In most circumstances, "Car-initiated, auto-reconnecting Bluetooth" is preferable to the alternatives.
Even if it does have bizarre and annoying UX failure modes.