For I know that people with blindness like to wear dark glasses is to protect them from ridicule because their eyes looks grotesque or deformed. And some blind people wear sunglasses because the light can cause intense pain. To protect their eyes from hurt, wear sunglasses can help a lot.
Most of blind people like to wear dark glasses for disguise. Commonly, some blind people usually roll their eyes, wearing dark glasses can prevent others from seeing their eyes. Besides, for some blind people, even if they have the same look as normal people, their eyes usually out of focus and always look in one point. It make them look dull. Wearing dark glasses can disguise their eyes. Still, there are some blind people wear glasses because their doctor suggest to. Most legally blind people are not 100% blind, they have some functional vision. Wearing dark glasses can also protect their eyes from UV rays and sunlight.
Actually a lot of blind people wear the dark glasses because of the high character of getting rid of the strong sunlight. They will feel better and comfortable when wearing the dark glasses which have higher ability to prevent from the uv rays in the strong sun lights. That is why they pretend to wear the dark glasses.
I can not make sure. But I think blind people wear glasses may because they don't want others know that he/she is blind. They just pretend to be a normal person and don't want to others look at them in a strange way. Also, some blind people may need glasses to shield their eyes from UV rays, intensive sunlight ans harsh lights etc.