The writers I know have a pile of unsold or uncompleted scripts and stories. They were experiments, or drafts, or betas (if you like). Often they're working on several things at once, sometimes just with friends for kicks.

They're driven to create also (characters, plots).

I'd say one difference is, it's easy to hold a steady job as a programmer, but as a writer you have to really work the business side. It does change the emphasis sometimes from creating to selling.