What do men gain

My question is what actually do we men gain from having sex?Cos as a man i've done it several timez and analyze the fact that women are gaining most parts of the men when properly checked.How can u as a man all u do is to stress ur self on women,u spend time in teasing them,taking them out,making them feel good,then after all this u've done u still go extra miles of wasting ur God given energy(sperm )on them.Yet they are not greatful that they have the men who do make them grow fatter by injecting in them our natural God given physical potentialz,they stil mess up.To me i came to realize that the only gain i as a man wil gain in a woman is when i get married and i wil see the products of my God given physical potential truely reflecting life.But never mind only the fun with which we men derive in women do also make us men younger,tender and happier.This callz for the questions that asks,what really do God almighty put in the body of a woman?Why do men derive joy in sex?Why must we men have sex?What do we gain when we have sex?All this are relevant questions and issues that needz answerz from naijapalz,b/cos after series of sex,as an intellectual i find no gain in it.Thankz.