Well...I must disagree with you on that statement. FC headlight assembly itself is pretty air deflective; encased with upper and lower bezel along with sheild behind the headlight itself.
Sleepy eyes are personal and appearance preference...and I strongly feel that airflow factor is extremely minimal to none.
As to headlight cover air scoops are concerned, it has some positive factor for fresh air flow into the engine bay, more specifically, cold air intake.
That's just my 2 cents
