From Science of Us:
You know you're at least a little curious. And so was Vanessa Brown, a senior lecturer of art and design at Nottingham Trent University in the U.K. Her research focuses on the meaning we assign to commonplace, everyday objects, and in an academic book that's coming out early next year, she explores the cultural and psychological relationship between sunglasses and our modern idea of "cool." In an email to Science of Us, Brown explained what her research has uncovered about why most of us look better in shades.
Because they really do make your misshapen face look better. Put on a pair of sunglasses, and voilà - instant symmetry! The dark lenses cover up any asymmetrical oddities around your eyes, and research on facial attractiveness shows a clear link between symmetry and our perception of beauty.
As an added bonus, Brown pointed out, sunglasses provide a kind of scaffolding effect, imposing the appearance of an external, extra-chiseled bone structure on top of your relatively softer-featured face.
Two other detailed reasons are also given.
(Score: 2, Informative) by Ethanol-fueled on Thursday July 10 2014, @04:54PM
They were en vogue in Southern California for a period of years, started by a resurgence of their use by Hollywood starlets, the rationale being that their size gave women a "bobbleheaded" look kind of like a doll. For the record, I never liked 'em either.
Now the only women who wear 'em are gaudy domestic Armenians and Arabs.
As far as the "hipster granny glasses" you suggested as being en vogue now, that's what the trend is here as well.