Why is sexuality a great gift of God?

Since ancient times, Christianity, particularly the Roman Catholic Church, has considered sexuality a great from God to be exclusively practised within the instution of marriage for the procreation of children. Also, over the centuries, chastity and virginity have been extolled as great virtues, sometimes even within the instition of marriage. The Church has given Christians the notion that sex is only for procreation and enjoyment of physical union is not something to strive for. The Church has also given Christians the idea that there is only one type of sexuality ie. heterosexuality. Anything other than that is completely out of the question and based on the Christian Scriptures, absolutely unnatural and therefore abhorrent to God.