Traditional masculinity dictates that men don’t share their feelings (with the exception of anger and aggression because that’s not a feeling that’s just being manly). Sadness, despair, loneliness, depression all will be commonly bottled up and left untreated which leads to deep-seated feelings of isolation. The cure has to be a change in social norms, including decoupling the ideas of being socially vulnerable with being feminine.

This is a gross generalization of the issue but it definitely describes my experience with it.