From how blind people were depicted in art throughout history, it doesn't seem like they wore anything over their eyes before sunglasses. A few examples:

Pieter Bruegel the Elder's Blind leading the blind from 1568

The blind girl by John Millais from 1856,

Blinds in the ditch by James Tissot around 1880's.

Two blind women, cartoon by Charles Dana Gibson around 1900's.

Sunglasses became widespread after Sam Foster started selling them in Atlantic City in 1929. Prior to this there were examples of handmade sunglasses but they seemed rather rare to find.

(Just a personal note: it seems that dark glasses became so widespread after 1929 that even Abing, a blind homeless Chinese street musician wore them in his only known photo from 1930's-1940's.)

I can only answer your second question. Blind peoples often have unnatural eyes mouvements. This can be upsetting to others they relate to. Dark glasses hide those movements - or lack of natural movements.