Because it's the only way to find some release... to write down the words...
Life is simple, but the human mind, our heart and our hormones (usually raging) make it seem complex and confusing.
And this society we have built for ourselves? To help us progress... It doesn't help either. It merely adds another variable to the logarithm called life we're already breaking our heads on.
Writing poems, penning down your thoughts or even just labelling your confusion by giving them words... it's all writing, it all means 'to create something'. Depending on what one wishes to create, they write a poem or a passage or an essay or prose, or even a book. It's an individual's choice. It's that person's choice.
The words come. Even we writers do not know where they come from, but they do.
And when they do, we write. On paper or tissues or newspapers or any means available to us, like desperate beings, finding an outlet, we write...
People write about a lot of things, feelings, things they're attached to, about people as well, when the only way they can bear the words to flow is rhythmic, maybe because if those intense words came out raw, they'd devour the speaker or the speaker would eat them up.
It's confusing even to us...why do we write?
Just remember, if you've ever been a muse in someone's work (be it a poem or prose or a song or a photograph or a drawn/painted picture), know that you've been adored and cherished and you've touched that person's life and left an imprint. One he or she wants to immortalize in the one way they know how to.
Do not take that lightly.
*Words mean something to us writers and blank pages make us ache, and even we don't know why that is...