I think this is due to the fact that we've become a more sensible and empathetic society recently. We have access to more education, mental health, etc. We have a better understanding of the importance of childhood as a developing phase for human beings, and just how vulnerable children are.
I mean, sixty-seventy years ago, the US still had apartheid; that's how much we have changed as a society (I'm not american, but there have been many cultural and social movements all over the world)