God created sex to be enjoyed within the context of that covenantal marriage between a man and a woman. He doesn’t restrict sex to this model just to be some kind of cosmic killjoy. He does it because he knows that within that covenant, a man and a woman can be naked physically, emotionally, and spiritually without fear of rejection. I don’t think we realize as a culture how damaging it is emotionally, not to mention physically (for example, STDs), to engage in casual sex. We may think it’s no big deal, but it leads to a lot of unnecessary pain and suffering for both parties involved.