Readers like to know what to expect from an author. You hear ‘I never read crime/sci-fi/fantasy/romance/horror or whatever’ and so it’s reasonable for them, when they find an author they like, to keep buying her books. And, if she suddenly replaces her ab-rippling young lover with a marauding dragon in scale-gripping lycra, they feel cheated.
Strange, really, because in all those and other genres, the books are populated by people, beings or essences that readers can apprehend, sympathise with, find interesting and compelling. Whether it’s a werewolf or a policeman in a red Jag, the characters feel, do and say the same sorts of things, as long as the reader’s been persuaded to suspend his/her belief and accept the reality of the tale
Most of my books have a crime element because I’m interested in motives and the whole shifting idea of good and bad. But I don’t want to be stuck in the police procedural bracket. I like writing other things. That’s why I’ve separated them into categories.