Some people are designed to only care about themselves. This means not their children, not their families but only themselves. These people care for their families and children when it benefits them. They are designed to not even notice this about themselves. They think it's normal. It's in their DNA. Unfortunately for them it eventually bites them in the ass. After running the same game on a few people they look at it existentially and realize they're pieces of crap but by then no one will help them or go near. Despite all the legal advantages society gives them a lot of people end up destitute and alone for this reason.