I used to want to be a professional writer, back when I had no idea what it would take to become one. I didn't know how many hours I would have to write, how much research into the publishing business I'd have to do, how difficult it would be to make any sort of living from writing.
There's also the matter that when I'm forced to do something, I don't do it. So if I'm forced to write in order to meet a deadline so I can get paid and not lose the roof over my head, it just doesn't happen.
Writing's just something that I enjoy doing, and since the only thing I write is fanfiction, I've readily accepted the fact that I won't be an official popular published writer.