Connecting a portable music player to car radios tended to go
* 3.5mm cassttee input
* FM transmitter input (for cars with CD, not cassette)
* 3.5mm aux input
Power was a 12V cigarette lighter.
During all of this the output from the mp3 lpayer was a 3.5mm device.
It was only relatively recently (say in the last 7 years) that most cars started getting USB and bluetooth sockets that took audio connections. Even then there are issues - my 2016 skoda's airplay doesn't play music properly - it frequently skips, I have to use bluetooth to get skipless sound, which means not using maps.
Having USB audio input as standard was even more recently than that - I hired a newish car about 3 years ago which had nothing by a 3.5mm input and 12V jack.
Even in newer cars, it's the same kind of choice reduction you see on phones, though. With a jack you can choose whether you want wired or wireless audio; without a jack you're still with wireless all the time, even when wired would be more convenient.
However I think use cases like air travel or just hanging out at home with a low battery are less rare. These can be partially mitigated w/ wireless charging, but when I use a wireless battery pack on a flight my phone and tablet don't do a great job actually staying in place, and necessities lowering the tray which is annoying
