Seriously, what is sex when the purpose is purely pleasure? Simply an elaborated form of masturbation, nothing else... You cum, your dopamine goes up, your money goes away.

However, when sex is done with someone whom you share some kind of feeling with, the senses are way superior and so is the purpose of that action. Cuddling, kissing and etc all rise hormones which help you bond with your partner and create a strong relationship, thus preparing the ground for having a stable family and actually producing something through this action which is not purely a charge of dopamine (or an elaborated masturbation).

So if you really want to benefit from the true gifts of sex, do it with someone you like to be with and intends to have a relationship.