Family code is driven by the desire that parties and children do not wind up on welfare. I don't want to pay for your kids when you can.You should not have to pay for my kids.
If you were correct, a couple of things would be different. For one, there would be no child support when both parents are rich. But the child support guidelines require multi-millionares to pay big support checks to other multi-millionares.
Single motherhood is the biggest source of kids on welfare, by far. If the family courts really wanted to get kids off welfare, then it would start by stopping giving child custody to single moms.