The way I see it, Science Fiction provides great flexibility with the background to the story. I literally get to invent a world, a concept or a technology. This allows me to focus on the reaction of the characters in the novel to their surroundings, and the effect that their environment has on them (which is what I am really interested in).
For example, suppose I want to write about the effect that overcrowding and associated loss of privacy might have on a society and the individuals within it. I either find an example from history - which may be difficult - or I invent a world in which to explore these ideas. In this context, think of, say, The World Inside by Robert Silverberg.