Often enough that race car drivers wear fire retardant, self extinguishing suits for when that happens. There’s even a rating system for how long a suit will protect you from second (and thus, third) degree burns when engulfed in flames during a vehicle fire.

Obviously, you don’t have to be soaked in burning gasoline for it to kill you, but if you are soaked in it, you can’t run away from the fire once you exit the vehicle. You, yourself, have to be extinguished, because you are the thing that is on fire.