There's some real snake oil being spouted on this thread.
We don't need to come up with theories based on some idea of evolutionary psychology. Actually, if men did always stay with their kids, it would be just as easy to explain in evolutionary terms, which shows what a red herring evolutionary psychology can be.
We are only one generation on from a society that says: raising kids is women's work, not men's. That attitude is still unconsciously engrained in society in all manner of ways, and it is only going to change over time. When a woman leaves or reduces work to raise a child, when a man takes on extra hours to compensate, when women praise a man for changing a nappy, when a man is criticised or considered wierd for looking after a child instead of working, you see that old attitude at work.
Same as when the man leaves, because the house is not his domain, and the family courts don't award him custody because the mother has been the dominant carer, not to mention when he gets away with not paying a cent of child support.
shebird
I think men have the ability to compartmentalise aspects of their life in a way that perhaps women do not. They are better at emotional detachment and so find it easier to walk away. They are also be selfish, self centred and needy and I think many resent the fact that their kids take precedence over their needs, let's face it some of them are just big babies themselves.
Charming. .
But you may have a point about emotional detachment. If society tells you that you are the second choice parent, some measure of emotional detachment is inevitable. Also, as the main breadwinner in my family (and yes, I am male) I find switching from work brain to home brain hard. Emotional detachment and compartmentalisation really helps me achieve this.