"The pen is mightier than the sword."
-Edward Bulwer-Lytton
Asking why writers write is like asking why people eat. There are plenty of reasons, but the most obvious is that it enables them to live. Writers live through their writing. The focus each writer has, however, differs between what kind of writer they are.
The Thinker
The Thinker writes to organize his or her thoughts. When they have just dreamed up a new invention or are working out complex ideas, they write. When they see the words looking up at them from the computer or paper, things just make more sense. To them, writing is a way of understanding the world around them. And sometimes they help others understand the world around them as well. Someone needs to type up those instruction manuals, right?
The Journalist
Journalists inform the world about current events, news and even their opinion of such happenings. They write to make the world aware of their surroundings. If it weren't for journalists, everyone would be running around oblivious to what's going on in the next town over,never mind on the opposite side of Earth. When journalists write, they have a sense of accomplishment, of duty.
The (other) Journalist
Ever keep a diary or journal? Many people have, and even they count as writers. Like The Thinker, journaling helps this kind of writer organize his or her thoughts. An entry can be a long, drawn out analysis, a blow by blow time line of how the writer's day went, a poem, a dream, or even just random ramblings. The (other) Journalist writes whatever comes to his or her mind for a sort of therapy. Simply put, it just makes them feel good.
The Author
Stephen King, J.K. Rowling, Edgar Allen Poe, J.R. Tolkein, William Shakespeare...the list goes on and on. They could all write for several reasons. The first being that writing is a creative outlet. They build a world most of us could never dream of, and make it a reality for their readers. To rope someone into that world is very rewarding, and lets the writer know that they are doing something write (and right). And that makes them want to write even more. It is like a drug. For writers and readers alike, you get so involved in a work, dawn has come and you forgot to sleep.
The Poet
Poets, such as the aforementioned Edgar Allen Poe, have a special way with words. They often write to create profound art. Or maybe they write to get a laugh out of someone. Many times they write as a creative outlet. Either way, poets are a special kind of writer. They are unique, and get something out of writing poetry that is inexplicable.
The Money Hound
Of course there is always the writer who only writes to make a living. They are good enough at it to pay the bills, and it's not a typical office job, so why not? The reward is in the paycheck. There is nothing wrong with this, but it just goes to show you that every writer has a reason for choosing that as their occupation.
All writers write for different reasons. For some, it's art. For other's, it's just a way to make ends meet. For me, it's the former, along with a combination of the other categories. Many people don't just fit into one.
I am a journalist who has a livejournal.com account. I write for therapeutic reasons. It makes me feel good to see a blank page filling up with words that not only help myself, but others as well. When I receive an e-mail from a reader praising me, I write even more.
I write to inform others. It is gratifying to know that I'm helping others obtain knowledge about their community. I like writing about the groups of people who don't get recognized for something wonderful they are doing.
I write for my future. While my job might give in to technological advances, making newspapers seem like a thing to only be remembered in the past, it gives me the experience I need to write in other platforms.
I want to write to create different worlds. Writing is imagination in movement. I want to be mentioned with other great writers this planet has seen. That is the greatest accomplishment, I believe, any writer can achieve.
Simply put, write is might. And that is why most writers do what they do best.