I can't speak for everywhere, but in my community and among my family members, the number one reason they want everyone to have kids is religion. Their god(s) tell them to have children, and so they do (my FIL has five!!!) They see fecundity as godliness, and so at best they see childless adults as confused or misguided, and at worst they see them as heathens and heretics. Most of my family are good people and understand the value of self-determination, even if they don't understand my reasons. But there are outliers; someone once told me that they were glad I wasn't having more children because I live a "pagan" life and my children would be punished by god unless I raised them into the church... No clue why they thought I was pagan, as I've always been clear about my personal dismissal of religion.

Wild.