[robchalmers]

As said above manufacturers have to guggle a lot of thinks when designing cars. In no particular order:
Styling,
Styling cues from the manufacturer 'face',
Customer acceptence
Crash test requirements
Regional requirements for things like head lights / tail lights
cooling/heating for extreme conditions
cost of repairs
ease of repairs
ease of emergency work (flat tires - wheel covers can be a b*tch on a side of a highway on a wet day)
and of course ........

WAF

well, JPAF joe public acceptence factor..... you'd be surprised how many won't go for a 4ft boat tail on the back or their sub-compact


All of the above though goes against what we've done at Bentley - where we've actually ran a competition for people to pen an aerodynamic concept car in order to help reduce our future fuel consumption
linky