Fantasy vs Science Fiction

Having read both fantasy and science fiction from a young age, I've always assumed that those who are drawn to this type of story would generally like both. I mean, what's not to like? So it has been a bit of a shock for me to see that there is very little crossover between those who read and like one of my books in one genre versus the other. In other words, very few readers read both my fantasy and my science fiction, even if they really loved what I wrote.

Zoya from The Immortality Game. Art by Stephan Martiniere.

Is it really so unusual to like both fantasy and science fiction? What would make a person read a book in one of these genres, and if you like it not want to read books by the same author just because they are in the other genre? I loved the fantasy novels of Ursula Le Guin, so naturally I tried out her sci-fi novels. I do admit that so far I haven't loved them as much as the fantasy books, but I still tried them. Same thing with Richard K Morgan. I loved his sci-fi novels, so I tried out his fantasy books. They were pretty decent.

How about you? Do you like just one of these two genres and not the other and if so, why?