I was scared of the dark, so when I was little, six or seven, I made up stories in my head to get myself to sleep (I still do this every single night), and one day I started writing them down. Then, suddenly, I began having strong opinions on things I was reading--whether or not I liked the sentence structure and if it was a style I'd like for myself. I went through a huge pretentious thing in high school, sure my writing was the work of a teenage prodigy. And then once I hit college I was severely humbled. Severely. It hurt, but I'm glad I don't walk around thinking I'm the greatest author of my time anymore. It's that fear of never becoming published that encourages me to reach out for help and to become better and to pay that much more attention to what I'm writing. I try to write the types of quiet, introverted stories I like to read, so I do think there are people out there who would enjoy my stories, and even more people who find them pointless.
The truth is, if every literary writer STOPPED WRITING from now until the end of time, there are so many books out there that the world would not know what it was missing, and thus would not care. Once you read a book, that's when you're glad you've found it. Unless it sucked...
Shorter answer: I have no idea why I write, but I think it's something my mind was pre-destined to discover, whether or not I had been scared of the dark. Even if I'm never published, there's nothing I can do about my inability to stay in reality for more than brief and undesirable intervals. ^_~