Hmm. I wonder if this flows from divorce in the previous generation. If you didn't have a father (or at least not one who was present), you may not have seen a model of how to be a father. When you grow up, you are less likely to see it as something desirable, and less likely to know how to do it.
To avoid misunderstandings and red herrings, let me make some clarifying comments. Yes, I know that a number of those who left would have been lousy fathers if they stayed - even abusive. And that makes for a lousy model. And yes, I know that many of those without fathers present find others who can model fatherhood to them, and even of those who don't, some of them figure it out on their own. I still think that, on an aggregate scale, the absence of fathers a generation ago at least contributes to this trend today.
In a farming society fathers and mothers have a lot of meaningful expertise to pass down to their children. And they work closely with their children for decades. Family time is intense and probably not exactly utopian, but intimate and constructive.
As a father to a kid in the urbanized 20th and 21st century, way less well defined and the role super confusing. My kid is unlikely to do what I'm doing. I'm out of the house at work almost all day, and they're at school. My spouse and I would live relatively separate lives, convening only after work hours. What am I supposed to be teaching my son? Most values will come from society at large not from home. How do I relate to my spouse?
It's not surprising there's a general disintegration of the family. Conservatives want to blame it on liberal values and lack of religion, but this is complete nonsense. The economic model changed, and the point of both marriage and the family changed as well. Forcing religion on your kids or getting all freaked out about family values and abortion won't fix it. The economic foundation of the whole thing is gone.