Because the politicians who suggest any such policy, when it gets to the point where people demand they explain why they're proposing it, either has to come clean, or dissemble.
The latter is obvious lying and deflection, and that's a PR disaster. The former is an absolute shitstorm. Single-parent celebrities that have five different kids by four different baby-daddies go on talk shows and Twitter, start calling you a Nazi. Whatever passes for newspaper editorials now days start whining for the next 6 months that it's anti-inclusive and undermines diversity. Invitations at colleges to speak at graduation are rescinded, some of your campaign donors stop taking your calls even though the mid-terms are coming up in less than a year. LGBT activists then crawl out of the woodwork saying that what we really need aren't two-parent households, because anyone can be a parent. We just need two-plus income families, and that poly-amory is superior because it can potentially bring four or more incomes into the house. Only cis-bigots really want just two parents there.
And then you back off. Not a battle worth fighting. None of this, even if it worked, could be milked for votes in an effort to get promoted from the House to the Senate (or the White House). And since it would be attacked from day one with the possibility that it might fail, why even try? It's far from a sure thing. All we know is the correlation, not the causation.
The latter is obvious lying and deflection, and that's a PR disaster. The former is an absolute shitstorm. Single-parent celebrities that have five different kids by four different baby-daddies go on talk shows and Twitter, start calling you a Nazi. Whatever passes for newspaper editorials now days start whining for the next 6 months that it's anti-inclusive and undermines diversity. Invitations at colleges to speak at graduation are rescinded, some of your campaign donors stop taking your calls even though the mid-terms are coming up in less than a year. LGBT activists then crawl out of the woodwork saying that what we really need aren't two-parent households, because anyone can be a parent. We just need two-plus income families, and that poly-amory is superior because it can potentially bring four or more incomes into the house. Only cis-bigots really want just two parents there.
And then you back off. Not a battle worth fighting. None of this, even if it worked, could be milked for votes in an effort to get promoted from the House to the Senate (or the White House). And since it would be attacked from day one with the possibility that it might fail, why even try? It's far from a sure thing. All we know is the correlation, not the causation.