The ratio of those two values shows, in my experience, that a lot of people are not very good at things they spend a lot of time doing, and are generally unaware of their own shortcomings
The average American spends 4.2 hours a week in the car. A typical 40 year old american has driven around 50,000 miles. For someone to continue to be bad at driving after that much experience, it must be a fundamental limitation on their capabilities for learning, thinking, or understanding. Drive to work any given day in Denver and you will see that a large number of people suffer from those fundamental limitations.
This article seems to present a world where most people the author interacts with can think critically about a complex topic, and are interested in learning or improving themselves. I wish I lived where the author lives, because I have had multiple jobs across multiple countries and never encountered an average population like the author describes.
I've always assumed the reason people don't get better at driving with that much experience is the reason people don't get much better at most of the things they do: they've never pushed themselves to the limit of their capabilities. While this can be dangerous in a car, it can be even more dangerous when you're put in an unexpected circumstance with no ability to respond calmly and correctly.