Because the article takes the very rational and supported by the article side that these mothers were actually founded in kicking them out.
> The article also simply takes for granted that it's a bad thing that these nuclear families do not stay together.
No, the article goes much further that that. It points out that upper-class and middle-class people like to pretend and promote that the nuclear family doesn't matter while themselves acting like it does.
The main thesis of the article is that modern culture is actually undermining the poor while being mostly posturing.
> You can't simply say that men aren't stepping up
It's a good thing that it's not what the article is saying then.