When we say fiction belongs to a genre, we mean that it builds upon familiar themes and structures. By assigning a genre — a slasher flick, or a comedy of manners, or a murder mystery — we shape the audience's expectations. Genre is a locus; it makes the rest of the explanation less surprising.
And this is the point. People like genre fiction because it's familiar; it can be read easily, or even mindlessly. Literary fiction, on the other hand, challenges the reader. Its goal, according to theorists, is to make the familiar feel strange:
[T]he essential function of poetic art is to counteract the process of habituation encouraged by routine everyday modes of perception. We very readily cease to 'see' the world we live in, and become anaesthetized to its distinctive features. The aim of poetry is to reverse that process, to defamiliarize that with which we are overly familiar, to 'creatively deform' the usual, the normal, and so to inculcate a new childlike, non-jaded vision in us.1
When we create software, however, our sympathies must lie with the genre writer. We want the text to be simple, unsurprising. We want our readers to feel a sense of cozy familiarity.