Today, the law serves the best interest of the kids and the mom. Dad is seen as the breadwinner, and thus the "paycheck" for divorcing moms who are showed the divorce brochure and the good deal they are being offered.
The deadbeat mom uses the custodial system and family law to not only get what she wants but to damage her ex-partner in the process.
I often pontificate that my ex-wife is angry because she didn't get the happiness she imagined by moving her cheese from one man to a different man. She got everything she wanted in the divorce: the house, the child support payment + insurance for the kids, and the 70/30 parenting schedule, and still she's not happy.
When one parent checks out their options for divorce, they are beginning the process of separation and exit from the relationship. And hey, if they like the divorce brochure the attorney lays before them, they might even start leaning into divorce.
My ex-wife screwed me in the divorce and she and the therapist that setup our 70/30 parenting plan knew it. They were not basing their plans on science, but on "what's best for the kids" mythology that has been perpetuated since my parents got a divorce 49 years ago.