Well smooth is sort of important but reducing the size of the turbulent wake is far more important. The patched together civic looks like it has a much smaller turbulent wake than any of the cars above. Look at the fuselage of a cessna, the front motor and windshield don't look to aerodynamic but the fuselage tapers down to the tail leaving a tiny wake behind it.
Have a look at a prius, insight, fit, even a mazda5, you will see that they begin to taper the back end to reduce the size of the wake.