I would disagree with cooling drag, and I would say it's primarily downforce. These cars aren't designed for normal use.
Downforce is not just about keeping a car on the ground... Nor is it all about reducing the force of wind resistance. It's about being able to transfer 500-800 horsepower to the ground.
Nascar has a CD of .4, Indy car's are even worse, and DTM race cars are worse yet. Super cars are often designed in a similar fashion, because their needs are similar.
"To be faster you need power, but there is a limit to how much power you can put on the ground. To increase this limit, force to ground must be applied on the wheels. Increasing weight can do this, but weight makes handling worse and require more power. So we need some virtual weight, we call it downforce and get it from airflow around the car."
Speed and handling require downforce and not a super low CD. Allowing for more power to the ground, overcomes a "poor" CD. At 200mph, i think a 1 ft square creates drag that takes 70 horsepower to overcome. This is why they have 500-800 horsepower. Brute force combined with downforce allow them to be "super cars".
"In current motor racing competitions, including Formula 1, DTM, Indy cars and Touring Car, aerodynamic downforce plays the most important role in the performance of the cars."
Quoted From:
Downforce
Hope this helps ya.
~C