Autoblog:

When Nissan was testing the Leaf, they noticed a fair amount of wind noise coming off the side mirrors. And with any [electronic vehicle], exterior noise is amplified due to the lack of racket emanating from under-hood. So the lights were redesigned to split the air leading towards the mirrors, eliminating buffeting and drawing a clear line through the atmosphere.

They’ll keep changing as they get quieter, just like they did when they got faster.