I think the theory is that every car that has an FM radio has it tuned to something. So no matter what, as soon as you put on the FM radio, it would have the audio.
Yeah, until you have a 5 year old (probably me in this case in the 80s) that plays with random knobs on the dash when they get in the car. Is it volume? Is it the tuner? We’ll know once the car turns on!