Men desire women and visa versa, families are formed and children produced. That is what God intended. Like any good gift, however, Satan is quick to pervert or twist it into something God didn't intend. Food is good, but it can lead to ill health when eaten in overabundance. Wine is God's good gift, but can cause drunkenness when taken to excess.
Money is good, but can corrupt the soul when worshipped.
And so on. Common sense tells us, however, that unrestrained sex leads to broken families, fatherless children, and general chaos. We don't see that view in God. We read in Genesis 2 about a man and a woman. This unity of husband and wife is the basic unit.