I think Cyberdemon is making the most progress in explaining the reasoning. It's all styling. Big wheels and a chopped look are the trends, muscle cars take it to the extreme.
As for the sources of these trends, I think the big wheels come from advances in tires and a desire to have a race car look. Of course, the first time you buy new tires, you will cry for a return to 14" wheels (like my Miata has btw).
As for the chopped look, I think it is driven by a mixture of paranoia of "others" and a desire to feel protected. Windows have been shrinking on all cars for the last 20 years. This is just the cutting edge, as is the H2 that Scott Bennett mentioned. On one hand it is aggressive, like a Roman military helmet. On the other hand, it is protective, like a welding helmet. Maybe the Jason goalie mask is the best example.
"There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper." - John Ruskin