The Huge Problem Of Shoplifting In Black Areas

If you don't get robbed they (steal you blind.) Etymology below.

"To "rob someone blind" means to rob that person as though he or she were blind and thus couldn't detect the robbery. The implication, as medica says in her answer, is that the robbery is likely to be thorough and devastating because the robber has no fear of detection and no need to act in haste. The usage originated in the United States and goes back to the 1890s, though it seems not to have caught on in published writings until the first decade of the twentieth century.

Here is the entry for the idiom in Christine Ammer, The American Heritage Dictionary of Idioms, second edition (2013):
rob someone blind Cheat someone in an unusually deceitful or thorough fashion, as in The nurse was robbing the old couple blind. This idiom may allude to robbing a blind beggar, who cannot see that the cup collecting donations is being emptied. {Mid-1900s}

The earliest instances of "robbed blind" that my Ngram searches of Google Books found is in a letter from Milo, of Des Moines, Iowa, published in The Western Druggist (October 1891):"