Exactly. Lots of instable mental health conditions that make driving unsafe(mood disorders, schizophrenia, etc) can onset in people's 20s with almost no warning

Exactly. Lots of instable mental health conditions that make driving unsafe(mood disorders, schizophrenia, etc) can onset in people's 20s with almost no warning, as well. A decent traumatic brain injury can happen at any time and most people never go to the doctor for those, too.