I find sunglasses odd. I can remember as a kid never, ever wearing sunglasses. I spent so much time outside i didn't really need them, my eyes were adapted to the sun, save the occasional day i spent all afternoon in the summer sun and i would get a bit of a "sun headache" afterwards.
Now it's common many people put on sunglasses when they go outside. Humans did not evolve to have sunglasses for a reason: we never needed them. Apparently adults go outside so rarely that now we do need them.
We live in Canada, so we go outside less than many other countries, so maybe our eyes aren't as exposed to sun rays, so are sunglasses less common in ie: California or the southern US? Do black people need them less than white people because black skin around the eyes/cheeks absorbs more rays/glare (think of a baseball or football player wearing "eye black" to avoid sun glare)