How does car racing contribute to advances in car design and manufacture?

Making a car go to its limits is easy. But making the limits higher is hard. So when you discover that a different type of suspension makes the car stay on the road, you might think "hey, if we modified this so it's comfortable, this could make out car much faster, and it would look really good to a buyer!" So they make some changes so the car is nice to drive, and the car gets some racing pedigree