With any auto manufacturer, you'll find that they will put all sorts of random countermeasures in place to delete sounds, farts, and other mechanical chatter. While they were probably aware that the baffles would rob a horse or two from the rear wheels, they knew that they would rather have a whisper-quiet system that could be sold to hundreds of thousands of customers without a complaint of an odd noise.

Take the Nissan Leaf -- the ONLY reason the headlamps look as silly as they do, is to alleviate the wind noise from the mirrors by adjusting the slipstream. With the silence of the electrical motor, the wind noise was simply too pronounced. We went through fifteen mirror designs before we simply raised the headlights -- problem solved. No idea on how much electric horsepower that gained/lost.