Read the other half at the linked site.
Obvious and Non-Obvious Reasons For and Against Casual Sex
1. Obvious reason to have casual sex: Feels good, instant gratification, etc.
2. Non-obvious reason to: The boost in self-confidence that comes from knowing that another person was attracted to you physically. Casual sex is about physicality. People need validation that they are beautiful. People who think they are beautiful are more self-confident in life. Self-confidence is good.
via Ben Casnocha: The Blog: Obvious and Non-Obvious Reasons For and Against Casual Sex.