Lots of cars don't have Bluetooth for audio. For example, we have a 2013 Mini that (somewhat inexplicably) supports Bluetooth for phone calls but has no provision at all for music over Bluetooth. But it does have a auxiliary audio input.

Neither of the other two vehicles in our household have Bluetooth at all, but they both have aux inputs. Bluetooth is a shitty workaround to intentional, anti-consumer stupidity. Just as almost every car (even cheap-O rental cars) integrated auxiliary audio inputs, Apple removed the audio output from their best-selling music player (the iPhone). And when gutless consumers allowed them to get away with it, everybody else followed suit and now we've regressed decades.

Twenty years ago I built an iPod dock into my car, into which I could plop my iPod (and later iPhone) and get power into the phone and audio directly into the stereo system. The phone charged, and delivered good audio quality. As a bonus, it did so without the need to dick around with two volume controls, since the 30-pin connector had a proper (fixed) line-level audio output that didn't vary with volume adjustments on the phone.

This is a level of convenience and performance that very few people enjoy now, and that is pathetic. Manufacturers have intentionally degraded so many of our consumer-electronics experiences with no payoff for us, and very questionable payoff for them.