The literacy test was to gain citizenship after you had already been granted permanent residency, so while they wouldn't be eligible to vote in federal elections, illiterate people would still enjoy almost the benefits and rights of any other US person. Almost anyone can learn to read, it's not that hard, almost every 5 year old learns to do it. If an adult in the early 1900's wanted to be a citizen, but were blocked by a basic literacy test and still didn't learn to read it's because they weren't interested in putting the effort into it (there are people with severe disabilities, that is a totally different situation and i'm not addressing that). Of course it's way easier to be born rich, but if you think someone who is poor but motivated can't learn to read you are insulting their intelligence.