Had some eyedrops today that made the computer screen and everything else up close really hard to see for a few hours, which gave me time to think about people whose eyesight is not the perfect 20/20. It turns out, there are plenty of those -- half of the American population over 19: "More than 33 percent were nearsighted and 36 percent had astigmatism, which causes fuzzy vision, the [research] team reported. Another 3.6 percent were farsighted, meaning they can see at a distance but not up close." (- Reuters, and here's the actual study)
Which means those who are in this half and are not wearing lenses or glasses have trouble reading whatever it is we are writing.