it's part of a general attitude that men don't really feel pain or take damage from blows.
Certainly, and that is problematic. I don't mean to downsize the reality of a man getting hurt.
However, the fact remains that women historically have been, and continue to be, the predominant victims of domestic abuse and sexual assault. As such, readers are far more likely to instinctively think of women as vulnerable and victims, and men as perpetrators of violence. Particularly because more people will have experienced, witnessed or known of women getting abused than they would have men.