I am not attempting to describe the world. I am trying to define the expectations we should have of the citizens of our polity. It has nothing to do with illiterate people manage not to commit crimes. I am saying that before we decide to get "big money" out of politics or we let people vote for the seven people who promise them the most shit, we should decided to put people who chose not to acquire basic skills that any human within standard deviation of average intelligence can acquire, when given 12 years of free education, into jail. It literally is not a literacy test for voting. It's an "are you a lazy piece of shit who is going to drag all of society down" policy.