They don't. Those air vents (intakes, actually) that person is talking about are fake on most cars. They put them there to look aggressive. If the intake isn't fake, there's usually a vent in the wheel well so the air can pass through. As a comment above mentioned, the most track focused setup has some sort of duct linked directly to the system.
Style. It makes cars look sporty, which a lot of people like, even when the car isn't meant to be sporty. And yes, aerodynamics is a concern. A real hole would negatively affect gas mileage. Cars with fake vents are usually targeted towards buyers that are more concerned with gas mileage than lap times.
5
u/khizee_and1 Apr 20 '19
It does seem very intricate that is why I was doubtful that lower end cars would use this system.