It is also often of form of courtesy. You don't want to burden single parents further by elaborating how damaging this can be for their kids, especially if you

It is also often of form of courtesy. You don't want to burden single parents further by elaborating how damaging this can be for their kids, especially if you have them in your audience and it makes it even worse if they take it to heart. So in that situation being polite and being honest collide like in many situations. There are some true believers, but they are far more rare.