Sexuality is a wonderful gift from God. It is more than genital behavior. It's the way we embody and express ourselves in the world. But we cannot love another person intimately without embodying that love, without using our bodies to love. And that does involve genital behavior.
Sexual love is for the purpose of giving and receiving pleasure with our most intimate partner.
It is a means of deepening and strengthening the intimate union that exists. This can only be healthy and good if our behavior is consistent with who we are and with whom we love, and when we are true to our own sexuality and orientation. In regard to marriage, it's important to remember that the Bible was written in a patriarchal culture that assumed men were in control and women were subject to them. Marriage was not an equal partnership, but a matter of a man owning a woman or women as property. Women provided men companionship, children and labor.