I believe that's a deduction instead of a credit but I agree with the main point of your reply.
Three of my four adult children are married with children of their own and pay very little in taxes compared to what my wife and I pay. My one son is in the same boat - married but with no kids. He pays through the nose too.
If I recall correctly, Clinton turned the deduction into a credit of $500, and Bush made it a $1000 credit.