I am told that I write because I have to. I am told this by others. Other non-writers. I don't think they quite understand the motivation to write or the need to. I don't write because I have to. I have other interests to keep me busy. So why do I write? Because I love to write. It is the clearest form of self-expression I've found and that's saying something since English is something of a blunt instrument when it comes to self-expression.
But there are other reasons too...
It is probably different for other writers so I will only speak for myself. I get these ideas in my head. Lots of ideas. They swim around like goldfish in a bowl and eventually one of them comes up for air. That's when I want to grab it and get it out of my head.
I need to get the ideas out of my head to make room for other things, like more ideas. So another reason I write is to clear my head. But that's probably the least important reason because ideas hit me like a meteor shower and if I didn't have a way to take notes on all these things I'd go mad.
No, the main reason I write is to tell a story and to share it. It is the sharing part that's key. Writing without sharing is like talking to yourself. Sharing makes the act of writing social and very, very human.
Storytellers have been sharing stories since mankind first learned language. Back then the stories were about the hunt completed or some myth to explain why the sky is blue. Nowadays, the stories are more complex but the need to tell a story is the same.
Unfortunately, sharing stories is more complex too. Oh, I can post text in one form or another on sites from here to China, (and in fact I've tried a few sites), but that doesn't guarantee a broad audience and doesn't compensate me for my work either. In fact, despite the technology at our disposal, the majority of readers do not leave comments or identify themselves. So this form of sharing is unsatisfying.
No, the type of sharing I'd like to do a close interaction with the reader. And the only way to do this is to show to a show, such as an author expo or convention and talk to each person. It is a slow process to be sure.
Perhaps some day there'll be an easy way to reach a broad audience.