Presumably it's been a problem since day 1. Meaning it was broken on day 1.
> But why can't my iPhone let me set permissions for the thing I plug it into?
There's the 'trust this device?' popup that should prevent the problem if you don't want the car to do anything with your device. If you want finder control, then from Apple's point of view, it's probably that this would needlessly clutter the UI, given that it shouldn't be an issue in the first place. Then again, I don't think Android supports finer controls either way.