Keeping sufficient distance doesn’t account for other lanes, where people could be entering or exiting your lane. Keeping all cars moving within 20-30 mph of each other make everything else more predictable. Saying that speed is not related to probability is just false. You can mitigate risks at higher speeds to a point, but higher speed is more risky just by the fact of human reaction times and that roads are not a simplistic system where the only factor is distance to the car directly in front of you.