Every now and then I come across an instance of that strange breed who don't read fiction. They may read books, lots of them even; and they may watch an occasional movie ("Oh yeah, I saw Avatar, and that was quite cool, though I don't really go in for that 3D shit."), but if they have disposable book-time they'll never read fiction.
The reason was clearly and lucidly articulated by a work buddy of mine, who, prompted by my question "Why not?", made a complicated compound gesture that was a mixture of shrug, head shake, general arm-twitch and an inarticulate mutter that might have meant something like "I just don't."
Reminded me a bit of what another, similarly disposed buddy of mine (a very intelligent mathematician/physicist) said quite a few years ago: "I just don't see the point." And then there's that silly atheist guru and wonderboy, Richard Dawkins, who told an interviewer that all fiction stories are lies and should be banned, initially from schools, and then people should educated not to promulgate these lies at home. The whole enlightened enterprise would be helped along by removing all fiction for young impressionable minds from libraries (and bookshops, I suppose). Ultimately we would only have 'true' stories, in the sense that anything not considered as 'real' by the likes of RD would have been eliminates from all stories.
Ridley Scott, in his recent flick, 'Prometheus' had something to say about that kind of scenario, and I'm inclined to agree with him 100%. Nobody's damn business what I believe to be 'true' but my own. Only my actions potentially are of any concern to the rest of the world.
Back to the original topic. The reasons given in almost all articles I found on the topic, some of which have a smooth rational air about them (might call it a 'Dawkins Finish'), are bogus. The real reason is a combo of reality-sclerosis (that's what you get when you pay too much attention to what you think is 'real' and therefore significant, but which actually might not be) and a lack of exposure to stories (not just 'literature') during one's formative years. Especially fairy and fantasy tales, which aren't only important but essential for the formation of a balanced human being.
That may sound like a huge generalisation. Maybe it is, and maybe it isn't. But in my experience people who didn't believe on monsters under the bed and fairies in the woods (or something ontologically equivalent, which by the way excludes most religious stuff, because that's something very different!) end up as adults without the capacity for at least considering one impossible possibility at least once a day. They also end up incapable of that magical activity called 'daydreaming', and that is sad indeed, even though they'll never know what they're missing.
They'll also end up 'old', which is probably the saddest thing of all. Losing the capacity to get lost in a story is a sure sign that a lot of other capabilities have also either disappeared or atrophied.