I own my car for pretty rational reasons: to commute to and from work, and to run other errands in and around the medium sized city I live near.
Quite rational reasons for why a driverless taxi won't work.
sandworm101 mentioned "People own cars for irrational reasons". I wanted to add some rational reasons for owning a car, beyond what RightMillennial wrote.
Many people don't have a car and don't need a car. The point is that there are reasons for owning a car beyond 'irrational' things like fashion and coolness.