People want headroom and legroom so that's what they are given. I guess any aerodynamic design to the front would interfere with safety crush zones, or would just be too expensive. Good mpg is not going to net the manufacturer any money once it's out the door, when people usually buy cars for looks and function.
Just like everything else in our grimey, consumption-led economy, people want what they're told.
The rise of soft-roaders and "SUVs" has everything to do with marketing and little to do with practical need; two exemptions potentially being demand from a growing (and historically unprecidently affluent) older generation who covet the accessibility of higher ride heights, plus the arse-about-face, unintentional result of the prevelence of speed humps in urban areas; which are less abhorrent to the occupants of large, long, heavy vehicles.
In addition we live in an ever-more hostile, divided and individualist society; where people increasingly value the "superiority" over other road users afforded by driving something massive with an elevated seating position.
Viewed from every other angle these vehicles offer only drawbacks; inferior fuel economy, handling, ease of parking, road visibility for other road users, survivability for third parties in accidents...
Most people willing to take the enormous depreciation hit on a new vehicle probably don't care about fuel economy and if they do base their decisions on official figures that likely bear little relevance to real-world performance.
In any case hydrocarbon fuels remain ridiculously cheap relative to the energy they contain / the impact of their use; thanks to the fact they're essentially freely-available natural resources open to anyone with the means to extract them... the real cost effectively subsidised by the rape of nature and the subjugation / exploitation of regions rich in these resources.
Sadly the rise of these nasty icons of conspicuous consumption is just another miserable example of the polar difference between the direction we should be taking as a society, and that we actually are thanks to the dominance of the usual negative human traits.
