Well a huge amount of people see the car as a chore, a way to get from A to B. If they all stopped using the car streets so that they are 95% more empty, the car enthusiasts would remain on empty streets. I think that would make them safer, you would need less lanes. It would be more fun and safe to drive on empty streets and only with other driving enthusiasts who are paying more attention than someone getting from A to B. (I write this as someone who lives in a region without racetracks.)