This is fairly simple, though the answers might not be. What drives you to write? This can be anything, from fanfiction to fantasy to sci-fi to romance. What makes you sit down at the keyboard or with that pen and paper and begin to form that world?
For myself, I just like the feeling of breathing to life a new world and people to inhabit that world. I have called it 'playing God' before, and I feel that term is a fairly good description. When you write, you can change history, the future, or the present. You can create a whole new living, breathing world with thousands of characters that are indeed out there, even if you do not write about them specifically.
Also, there's just something cool about the world you create, and the characters. You know them better than anyone else in the world, know every aspect of their lives. It's just a cool feeling.
So tell me, why do you write?
Velkyn