Academic writing is incredibly different from creative writing. My thesis is currently 14 pages and utilizes a good dozen sources, and I've been working on it for months. Months of creative writing gives me five times as many pages. At least. And yet they really aren't all that different. All of it is personal and all of it requires individual thought. But academic writing, at least research based academic writing, requires you to build on what others have said and to incorporate their thoughts into your own writing. Fiction writing )and poetry for that matter) is all you. Maybe that's why it comes more naturally to so many of us. Yes, it requires research, but the writing, the story itself comes from us. Everything we need, we already have. Writing a thesis on the other hand, well, I need a lot for that, haha.