Because the words will kill you if you don’t.
Unexpressed stories tend to eat you from the inside until all that’s left is a withered husk. And you won’t get back your vitality.
You see all those old people, desperate to tell you their unwritten stories? That’s because they looked in the mirror and saw the words clawing to get out, tearing at their flesh from the inside, gnawing at their muscles until they became too weak to stand without assistance, and sucking the moisture from their skin until they became wrinkled prunes.
And the old desiccated human husks know that if they could just tell your their stories, they might not revitalise themselves, but they can stave of death for another day and maybe inspire you to look away from that television set that sucks away all your creativity, and sit down and write. Write to express yourself, to tell your stories, and to let out all these stories so they will stop haunting your dreams and start haunting other people’s dreams.
And then you can finally lay down to sleep, huddle beneath the covers, knowing the monsters aren’t under the bed but in your head, and that they’ll only be mollified for a day or so, so you’ll have write again tomorrow, but at least you’ll be able to sleep.
But if I’m wrong, and you’re already too numb to feel the stories gnawing at your insides with their blind craving to be set loose on the world, then perhaps you have already become that walking empty husk, and perhaps there’s no need for you to write your story.
In that case, forget everything I said.