Every aspect of a cars shape must meet crash standards, lamp size standards, airbag deployment, crush zones, ect. Add the aerodynamics for fuel milage concerns (CAFE requirements) and you get a fleet of almost identical cars with hoods too short, windshields layed too far back, cowl to dash lenghts far too short, and stubby deck lids way too high. Just add a grill and make the lamps have wierd points going all directions and a styists job is done.
Even the Porsche "911" (yes I know it's really a 996 or something like that now), Dodge Challenger and Ford Mustang, which are the best looking cars made today, have many of these compromises keeping them from being really great looking cars.
What about all the cars not made in the last 40 years without guardrail bumpers or cafe regulations? There are plenty of cars made around the world that never had to conform to these. I know, opinion and all, but you are seriously going to say that a Challenger or a Mustang are better looking cars than a 458? An Alfa 8C? Maserati Gran Turismo? GT40? C'mon.