The Orthodox position starts off wrong with the very first sentence: "Sexuality is a gift from God, as we read in the book of Genesis." The book of Genesis has zero understanding of how anything, the universe, sun, stars, planets, plants, animals, oceans or potatoes came into existence.
So, to get it right, sexuality is one of the ways that nature ensures that life continues -- and since that continution is one of nature's higher "priorities" (sorry, I hate anthropomorphizing nature), it is high on the list of urgent faculties. In other words, we all want it -- and we're not all thinking about babies when we're doing it. In fact, we almost never are.