Many times, we buy new vehicle because the look is outdated, paint faded, interior worn out, overall impression that you are driving an old car. This is despite promptly maintaining the car as per manufacturer requirements/schedule. Here you have a car that has an "old" body and pristine from the "inside" mechanically.
Especially for mass-market type of vehicles , it maybe beneficial to consumer to have the ability to purchase the replacement of just the body of the car, while retaining the same base platform?
Different kinds of car-body would include sedan , coupe, pickup, convertible, etc..
Modular design can also offer lots of creative ways a customer can be "unique".
Many advantages here both financially and environmental I see as well.