That's a poor "domestic" example since it's a Le Mans GT car. The radiator on those is also mounted in the rear, or is now, or was. Not sure what else is up front or if they're just controlling the air. Escaping air = using it. Of course just allowing it to run free would not serve any real aerodynamic purpose.
A cowl hood on a muscle car can serve the purpose of getting air into the carbeurator, that's what I always thought they were for anyway and mentioned above.