Ponder no more where the mentality comes from about remaining childless. Look no further than the self-titled "Judge" Rutherford, the theocratic autocrat man who remains a stain and an embarrassment to every reasonable-minded JW:
One of his last books - before he became one of the millions then living who died in 1941 - was titled, "Children".
While that book was obviously addressed to children, its central message was the importance of giving one's all to preaching the kingdom message "in the months remaining" in this old system of things.
It hammered the need for young people to defer marriage, and if already married, to remain childless.
That book was quietly side-lined within 5 years of its initial publication.