I do agree that there should maybe be an option for a "generic" rider and passenger who are wearing goggles and leather caps, and possibly even scarves to deliberately obscure their identity.
Reason being, I expect many purchases to be made for Pulp Alley. Well, in PA, you have rules for regular characters using vehicles of all sorts, but you can't possibly sculpt a hundredth of all the possible riders... but if there's an "unknown" rider + passenger pair, then they can stand in for any PA character who hops on a bike and takes it for a ride in the course of a game.
Other games have different considerations of course.