People choose to have sex for a variety of reasons – to connect emotionally with others in a very intimate way, to experience physical pleasure (including, but not limited to having an orgasm), and in the context of heterosexual relationships – to create children when they’re ready to be parents. The only way to know why someone is having sex is to ask her. You might be surprised by the answer! If you’re having sex with someone you should feel comfortable asking her (or him) this question.