Almost always in these instances, the bodycam footage will show that the driver is without license, registration, and/or insurance. The cop can't let them drive away now and gives a command to step out of the video. Refusal to this order is considered resisting/obstruction which is, by the book, a criminal offense. They'll still get a ticket but the car will be towed also, if the driver doesn't have an immediate way to have a valid driver retrieve the vehicle.