Most vehicles have a radio. Most vehicles do not an 1/8th inch headphone jack to connect an audio cable to. Neither do many vehicles have an iPod, iPhone or iPad dock connection. To those who wish to listen to music or spoken word in their cars, trucks or any other motorized equipment I suggest you go to a car audio store with said vehicle. Sales people will detail your options. Understand that nothing expensive is required for this. An audio-in jack will do and a lot of the cheapest CD decks have it built into the face. Maybe a couple hundred dollars with installation?
I agree that FM transmitters are pretty bad if you want quality and reliable music.