Pubertal stress, sexual enticements and peer pressure motivate people to cuddle, kiss, satisfy their curiosity and rub their genitals on someone. All of that, occurring in the same individual at the same time, creates a compulsion so great that humans have mistaken it for the will of goddesses, the temptation of demons and an irresistible animal instinct.
When, to all of that, are added the beliefs that people can not resist instinct anyway and that there is something wrong with them if they do, it is highly likely that humans will mate indiscriminately and that their behavior will be reinforced with barrages of hammering pleasure. Through repetition are created stimulus-response connections among increasingly large arrays of sights, sounds or touches and the sexual mechanisms of the body so that sexually active humans become more sensual as powerful emotions take over where reason has left off.
Intercourse, masturbation and sexual fantasies create a circuitous "reasoning" wherein natural opioid reinforcement occasions renewed cravings that trigger opioid rewards which promote cravings ad infinitum until people actually believe there is no option in life and come to depend on that process for entertainment and distraction.