It isn’t just a matter of God wanting more babies. Unlike condoms or the pill, abstinence doesn’t turn a sacrament between a husband and wife, meant to create life, into a self-serving recreational act.
By your reasoning, a couple incapable of conceiving a child should not have sex? Post-menopausal women, those with infertility issues, etc. have sex for a number of reasons - conceiving a child is not one of them. I suppose you might call it recreational sex. Self-serving? Why? It involves mutuality, love, concern for the other - all certainly sacramental, if by sacramental you intend a means of experiencing grace.