"Why can't you give up untold amounts of money, free time, peace/quiet, lack of stress, and freedom so I can have my grandkids around for a few hours a week? Stop being so selfish."
Also, why don't you want to bring new human beings in a world that we have destroyed, that will struggle when I'll be gone and you'll be powerless to help? So selfish
These are also the people who either disappear anytime their kids need help with the kids, or else were such terrible parents they're the last person on earth their kids would leave alone with their children.