"Literature was not born the day when a boy crying "wolf, wolf" came running out of the Neanderthal valley with a big gray wolf at his heels: literature was born on the day when a boy came crying "wolf, wolf" and there was no wolf behind him."
-- Vladimir Nabokov
In other words, literature was born when somebody made up a story.
This quote could also be talking about the origin of theater, though -- but then, both theater and literature came from the oral tradition of story-telling. In my case, both off-shoots have influenced the type of writer I am. I did a lot of theater in my youth, and to this day, I approach my stories from a "theatrical" angle. First and foremost, I want my stories to hold the attention of my audience, to be dramatic and interesting and entertaining.
This theatrical basis holds true in more practical ways, as well. My first drafts are mostly dialogue and "blocking" (moving the characters about the stage). I learn about my characters through dialogue -- I need to "hear" them speak before I have a really solid grip on them. I don't describe the setting much in a first draft; in fact, I have yet to completely visualize or map out the castle where most of the action takes place in my current work-in-progress. Description and details will come in the later drafts, after I've distilled the dialogue (cutting and/or combining scenes where necessary) and made sure I've got the activity in the best possible general location. I suspect this is why I'm most comfortable with "one set" stories, rather than "road" stories, where the hero and heroine go from place to place. That requires a lot more emphasise on description. (I do note, by the bye, that Nabokov described the wolf, so clearly, there is a very important place for description. It's just that with me, character comes first, description of the physical setting second.)
So why not write plays? For one simple, yet important reason: in a book, I can detail my characters' thoughts. Readers, hopefully, get to feel they know and understand my characters in a more profound way. If I've done my job really well, my characters will become real people, the way the little boy convinced the villagers that there really was a big gray wolf.