Humans are the first animal to have a limited ability to control reproduction, but only limited. There are those who have managed to be celibate their entire lives, but we aren't the descendants of those people. We're the descendants of those who had no self control. Sex is a 3 billion year old tradition and it's not easy to break the worlds oldest tradition. Men are from the Earth.
Women are from the Earth.
People are having sex all the time. When we're not doing it with someone else we're masturbating. Most men ejaculate daily. This is the bodies way of getting rid of old sperm and making room for new fresh ones ready to get a woman pregnant. Women do the same thing so as to clean the lining of the uterus walls and to stay horny so that she'll be ready when the right male comes along.