> I've never heard it discussed by anyone that a badly maintained car is a danger to anyone other than its occupants.
That is surprising, because it should be fairly obvious that if a car has brake failure, it could be lethal to anyone who happens to be in its path. Same goes with catastrophic failures of the steering system, although those are perhaps even more rare.
There is a weird logic to all this. Air quality makes a noticeable improvement in everyone's lives and, paradoxically, driving is so phenomenally dangerous and so unavoidable that people don't worry about the very minor factors like the one in twenty who isn't paying attention to their brake pads when assessing that risk.
It might be that the high-pitched squeal built into brake pads to notify people of impending doom is actually doing its job, though.