The type of person who buys a brand new car probably likes a brand new car (new features, status, reliability, etc) and that doesn't change after a handful of years. Or the other way around, the type of person who wants to maintain an older vehicle is probably not the type of person who will buy a brand new car.
Obviously there are exceptions, but the used car market is much larger than the new car market so most are selling.
Obviously there are exceptions, but the used car market is much larger than the new car market so most are selling.