This is the joy of FANTASY. Not the genre, but the act of fantasizing, of day-dreaming, of taking a break from reality. The mind provides a rich tapestry in which we can weave all manner of falsehoods for our amusement, curiosity, and yes our titillation. It's a playground, a safe space where we can indulge in the things we'd never allow (or indeed never actually want) in real life.