Anecdotally, I didn't have a car until I got my first job. Not everyone has parents that can just buy them a car.
Anecdotally, I had access to my family's car on a pretty regular basis unless my mom had specific needs for it. I was a hardcore introvert and took advantage of that way less than I could have, but it was explicitly available.
I agree the stat is from 15-24. But I hypothesize that it’s as much about how kids learn to socialize before 15 that has a big impact later in life.