I've always wondered why people always lump sci-fi and fantasy together, given that they're totally different genres. It makes it really difficult to browse departments (online or off). And there aren't even that many crossover writers to justify the mix, in my opinion.
I mean, I can understand it in a way (they're both stereotypically geeky boys' subjects) but to me it's like putting crime and horror together because, y'know, people die in both. Makes no sense.
Does anyone know why - either logically or historically - they get thrown into the same box?
To me they are very different. SciFi is just that, fiction based on science, usually set in the future. Fantasy is anything BUT scientific, it involves magic and the supernatural and is often set in the past. As a scifi fan, it always bothers me that the shelves in the library that are labelled SciFi are full of stories about wizards and mystics. And judging from some of the cover art, they seem to be aimed at women, not geeky boys.
There are people who like fantasy, but not science fiction. There are people who like science fiction, but not fantasy. But there are a large number of people who like both. I personally know more people who like both genres.
The two genres actually have quite a bit in common, in my opinion.
They take place in a world different than the one we live in. The exotic setting is a big part of the appeal.
Fantasy monsters and SF aliens are a lot alike.
Non-human characters are a common factor as well. The non-human part makes them interesting and exotic. But they are close enough to human that we can talk with them, be friends with them or even consider a romance with them.
There is a common saying in the SF community that sufficiently advance technology is indistinguishable from magic. Take a look at some of the things in Star Trek. They can teleport. They can create food instantly. They can revive someone who is technically dead. They have ships that can appear invisible. It seems a little bit like magic. In fact in a fantasy setting the same things are done with magic.