I don't think I've ever met anyone who had a baby, but then failed to love that baby in some fashion, even if only instinctually.
Most (childless) people can't understand how quickly and totally one becomes attached to a child until it happens to them.
It is instinct. (The very small percentage of women who kill their children at childbirth are mentally deranged.)
I'm not talking about the extreme cases where women kill their children. I'm talking about parents who have children and then hand over their raising to someone else---be it day care or society in general. There are parents who don't have the "instinct" you are talking about. Their career and their search for more and more affluence is much more important to them than their children.
I've seen it too many times, even in my own family.
I think it's great that you have never met anyone who failed to love their baby once it was born, but it happens more often than you realize, and, to be honest, I blame most of the ills of society on that fact.
The news is filled with children put at risk by their own parents every day.
The news is filled with children who are murdered by their parents are due to their parents lifestyle every day.
I wonder how many of them had the instinct to pass on child-rearing, but for some reason or another (selfish?) decided to have them any way.