Women usually get custody of children because they gave birth and it's generally assumed that mothers have a stronger attachment to their children than men. Also, it's still considered the women's role to take care of children while fathers usually do activities with children that include games and fun, women are expected to make sure kids are clean, fed, and so on.

Single moms are becoming more and more common because in communities in which poverty rates are up men are more likely be in prison. Single moms and children are the most at risk people for poverty, it's sad but true.

Also, I think that women have become more egalitarian and have more financial freedom than they use to so it's more common for a women to leave her husband if she is discontent with the situation, while before she was just kind of stuck with a horrible husband.

To be honest I don't think the men are getting worse per say, I just think that women just don't put up with it anymore. I mean if you think about it, it's only recently that spousal rape has even become a crime (in the U.S), it's more of an awareness then some sort of plague that hit families. Or maybe it's both i don't know.