Many cars have this it like belt and suspenders as hood vibrates across dissimilar metal copper wires etc it builds voltage sort of tesla effect. The grounding diverts the voltage to battery .this is rare but some engineer thought it can happen . The
carb vapor locks gas fumes you rase an ungrounded hood touch the
carb if you wake up you might be in the hospital missing a few fingers at best. 1 gallon of gas equals don't got me but I think its 11 sticks of dynamite. Ihave personally see a dip stick blown through a hood. Newer cars don't have them except throttle body injection . Because gas vapors don't get in engine compartment normaly . Could help radio also because you don't want random voltage going through it.