the obligation to reproduce?

During Torah study we've been discussing the part of Leviticus that covers permitted and forbidden sexual relationships. Twice in the last three weeks someone has asserted that the purpose of sex is procreation. (I disputed it the first time; I didn't do so again this morning.) Then, this afternoon, I read an article in Reform Judaism, from the chairman of the national board, about how our population numbers are dropping and it's because we aren't giving priority to having kids and that's a critical mitzvah because we'll die out otherwise and blah blah blah. (Part of "blah blah blah" was that people are too concerned with their careers and not concerned enough with marrying early and reproducing.)

Nonsense, I say. ( rant ahead )