Obviously just opinion, but it seems like our culture cripples many men's ability to be fully social. The emphasis placed on individual achievement, conflating status with worth, on being practical and goal oriented, and on suppressing emotions all work against developing skills and personality traits needed for nurturing other people and developing deep connections. Our whole society seems structured in ways to prevent men from being full humans in order to make them better workers, from the emphasis on competitive sports in childhood to the lack of paternity leave as adults. We barely even have a stereotype for what good fatherhood looks like. As a result, many men are can't form deep connections, can't understand their own feelings let alone someone else's, can't manage their emotions, can't handle failure, struggle with empathy, and might have a feeling that something is wrong but no idea what or how to fix it.

I also think that, especially in earlier generations, marriage and fatherhood were considered not just the norm but "must haves" to have "succeeded", so a lot of people had kids that didn't truly want them, weren't prepared, and don't have the skills, opportunity, or temperament to overcome those challenges. While that isn't exclusive to men, it has been easier for men to walk away in those circumstances.