This was then supplemented in the car with a cassette tape adapter that included an audio jack. [0] It was pretty sweet, all things considered. Tape decks started to vanish from cars at about that time, and those FM transmitter adapters that would plug into the cigarette lighter and broadcast on a radio frequency were really crap compared to the direct jack. I would argue I didn't get that same level of ease+fidelity of pushing MP3s to my car stereo until I directly installed a Bluetooth stereo into my car 15-ish years later.
[0] example: https://www.amazon.com/Arsvita-Audio-Cassette-Adapter-Auxill...