Not all cars have low mileage in Japan. You do get some quite high mileage vehicles over there too. Having said that, they do have a lot of low mileage ones too! The national average is about 5,000km’s per year in Japan as opposed to our 20,000-25,000km we do here annually. Why? Public Transport is incredibly efficient over there so most people won’t drive their car to work each day.
Along with that, tolls are horrendously expensive and if you were to drive you’d never find a park anyway! There’s also the difference in size between Australia and Japan. We are around 20 times bigger than Japan so the amount of ‘highway’ mileage we accrue here doesn’t really occur there.