grey

ok...i have a small question on aerodynamics for cars:

in fluid mechanics, we studied the flow of air past an airfoil, which is designed to reduce drag (and obviously lift has a lot to do with it, but that is irrelevant for me now, so i am ignoring it). My question is that why aren't cars designed that way? that is, 'fatter' at the front and 'sleek' at the back? in fact, i seem to think that they are designed in the opposite way...why is that?