Cars, like human faces are iconic visual objects, with immediate, familiar recognition. As an artist, if you screw up a human face, no matter how realistic the rest the image, it will seem less realistic or poorly done. If you get the car looking recognizalbe and fairly accurate (especially with metallic highlights and shadows), the rest of the image will work. Being so iconic, cars are frequently replicated by vector artists.

However, there are no car illustrations in my portfolio - I'm not into cars, per se. Illustrations of humans, illustrations in reference to pre-20th century styles and maps are all that you'll find in my portfolio. So not 'everybody' has a car illustration in their portfolio...