Why do we write?

I tried for many years to break into the writing market, not knowing what I'm doing makes it pretty difficult. I mean I know how to write, I'm writing this, so I must know how to write, now whether or not I know how to write well, is another matter. I'll let others decide that for me. 

Outside of these blogs, five all together, a handful of magazine articles, I have not written much I wanted others to read. I read and read about writing, prose, fiction, character development, poems, you name it. But perhaps the best advice i received about writing, is perhaps the simplest. 

The best thing for writers to do is to write. Write, and then write some more, write when you don't know what to write about (which is exactly what I'm doing now). Write everyday, a little or a lot. But write and write. - I decided to do that, and I have been amazed that when I write, I am actually writing. When I sit down to write, I find that I am actually writing, now I know that sounds ridiculous, but what I mean, is that when I make myself write, I find that the words come easier, the characters begin to live - on the page and not only in my mind, and the sentences seem to flow. - 

The biggest problem I have with writing is multi-faceted - finding  new topics - and finishing one work before starting another one. I get 2/3 finished with a piece and a new idea strikes and off I am chasing that idea, leaving the old one to sit, gathering electronic dust waiting patiently for me to wander back into its file to finish. - Some have sat for years, some will never be revisited, others will be finished - Which leads me to the newest issue i am facing as a writer. 

How do I move from a writer to an Author? Where is that line drawn? what are the requirements to make the transition? I have two completed Novels, two distinct works of non-fiction I need and want to get into the hands of literary agents and/or publishers, but i have absolutely no clue how to get that done. Also I have one work of non-fiction finished and two others almost finished. - Does it do me any good to write these and not have any way to get them published? Will my family be my only audience? Does it matter as long as I write? 

For me it does matter, for me I have something to say, some things i want to share - which means someone needs to read it. Does it do any good if I am the only one to read it? does it accomplish anything outside of maintaining sanity for me, if no one reads it? 

I want to be able to walk into Barns & Noble, Books-a-million and see my work there, even if its on the discount rack, at this point I really don't care. I have something to say, and I have to say it, - I have to write. I have to write, and write and write. As someone said, (I forget who) I write because I must.