I feel like I'm going to be berated if I give the obvious answer of "people don't care about reading," so I'll say the following instead:
Reading is
hard work. I can't say anything about adults who don't read (perhaps it is part of that same common childhood trauma) but children may closely relate reading to school and intelligence. You read at school. You read
aloud at school. You are
graded on your reading and comprehension. Fast-readers are smart, confident, they get good grades, and are seemingly favoured and praised by the teacher. Slower-readers, in comparison, feel humiliated when they don't match up to their grade level, and in the end just stop trying.
Reading for school (IMHO) ruins any book (whether or not it is in your taste). You are given a time-limit. You are asked to analyze and give your opinion. Then you're told that your opinions are wrong and that you've failed English (well, maybe not failed, but your grade isn't proportional to your effort. Further, you've wasted all that time reading a book you didn't want to read when you could have read something else instead!). And (if you think about it) reading by itself isn't that rewarding (There's nothing tangible. Your "rewards" are far-off and aren't tremendous.) You always hear about people who can finish a book within
days; a book that would take you
months to read... By then the story is drained of all colour and you move on to something readily gratifying or more productive.
So, of course some children will not read without incentive. But books do not gain much (or any) publicity, and most kids have neither the patience or the care to go through the shelves to find something they might want to read.
I don't think this is attributive to lower literacy, though. If anything, with all children getting standardized schooling (which could be good or bad depending on who you ask) the literacy rate has never been higher. Ever. In all of human history. Yes, the education system can be better. Yes, media and technology is a huge distraction. So many factors to consider, yet the student who can't spell seems to be more an anomaly in this whole mess than the product of a lack of reading.
P.S. When people say they don't really like reading anything that's out today, I can't really say that I blame them. There was a time when authors "once knew better words, but now only use four-letter words."
......... I'm kidding... Geeze, I'm so bad at jokes.