Teens also have better eyesight. I used to read a lot of paper books when I was a kid. By the time I got to college, the only thing I read were textbooks, because I hated squinting at tiny print. Publishers have an incentive to be stingy with print size, since they can save money on paper. I’ve started reading more books again on my computer, because I can scale the font size to 24 and there’s a backlight.
