I'm in my 30s and I don't have a drivers license. You don't need a car at all in any city that's built around public transportation. I've lived in Tokyo for many years, the greater metropolitan area has something like 38 million people, and I think a majority of households does not own a car in the prefecture. God gave us two legs, they work wonders between train stations.
You still need cars for going from point A to the train station and from the other train station to point B.