He wasn’t. He dealt with that issue at the same time he defined marriage and spoke against divorce. Jesus clearly taught that divorce and same-sex marriage are not intended by God. It hasn’t helped that many Christians abandoned marriage long ago by supporting the legitimization of divorce. From today’s mass readings:
Jesus defines marriage as the indissoluble union of one man and one woman. Divorce was permitted under the old law “because of the hardness of your hearts”. Aside: what does it say about us as a society that we are back to the old law of Moses?
“Some are incapable of marriage because they were born so.”
Marriage is a vocation, first and foremost. One man and one woman is a prerequisite to marriage, but assuming this is satisfied, a man and woman must also be called by God to marriage, in the same way that a man is called to be a priest or a woman is called to the religious life.
This calling necessarily includes an openness to the gift of children, which is why artificial birth control — or even NFP, if used improperly — is a serious impediment to living one’s marriage vocation. By choosing to say “no” to the gift of children, even temporarily, we are also saying “no” to one of the principal vocational aspects of marriage.
Marriage is not a calling for now, until someone or something better comes along, or for as long as my needs continue to be satisfied by my spouse, or for as long as we both consent to being married.
Jesus doesn’t deal in exclusive proscriptions. He isn’t a walking book of Leviticus. He speaks about Love and Mercy. As the Word that is Truth itself, He speaks about what things are.
Jesus’ words on marriage are plain; they have to do with the truth of what marriage is: one man and one woman, who each leave their mother and father, and unite to form one flesh — reflecting the unitive, procreative and donative love of God — welcoming the gift of children and preserving the union for their benefit and security, for life until death. Amen.