Possibly on to something here. There's certainly people doing well focusing on their niche. Then again, not all of them seem to. My philosophy, which may be completely off here but it's the only one I got, is write whatever sparks interest and excitement in you. And maybe it'll do the same with others. Maybe not. Neither will it if you force yourself to stick to one narrow niche/style if you're not a one-style type of person. :)