I had a table read for some scenes from the Life Ends @ 30 script recently and I was asked why I wrote this story. My reason for writing it being that I was feeling many of the emotions when I turned 30 years old. The madcap comedy is more of an exaggeration, but the idea of being an adult when you're not quite ready to be an adult was present in my mind when writing.
So why do you write anything? Move writers are introverts. Most. Not all. To an extent, I keep a lot of my emotions and feelings to myself. But I have to get them out somehow. Writing helps with that. Much of the stories, while my imagination may run wild, are rooted in what I'm feeling or thinking at the time.
I'm not going to pretend that I'm searching my soul with everything I write. Some things I write because I think they're funny (Many of the sketches I write) or because I love historical adventure stories (Kiddo) or because I always feel things happen for a reason so what if that was a result of someone killing for my happiness (The Best of Intentions).
I don't write because I can. I don't write because I want to. I write because I have to.