Civilizations rise and fall. What happens after 500 years of this suppression that the human race no longer has access to high tech (thermonuclear war)? We've just doomed millions of children about to be conceived during this period. And while it would be a minor issue compared to an event of a societal collapse, it's still another form of misery we have inflicted on future generations.
You do know we have a "doomsday vault" holding most (if not all) the seeds for the crops we grow, right? The idea being they serve as an original genetic source in the event we genetically engineer our plants to extinction. It's a way of saying "oops, we hit a dead end and now need to walk back and start over with original source material". We don't have that luxury with human beings let alone other animals. People aren't Cabbage Patch Kids; you can't grow them in the ground. With seeds at least, anyone in this world can plant them should the world turn post-apocalyptic.