I believe that was with the old vehicle system, i'm not sure if it is still in effect.
Actually vehicles will not be removed or at least need not be, because in the previous script there was only a select number of each vehicle. Inactive players had vehicles removed, so that others could go find those vehicles and have the opportunity to own them. Whereas now there is an unlimited supply of each vehicle available on the server. Which means there is no real need for them to be removed from anyone.