I think that Western masculinity has just been worn down by public education and helicopter parents. From a young age boys are punished or medicated for traditional male behaviors that society no longer desires. Meanwhile, poor or immigrant males that lack access to education or have absent parents are more likely to embrace natural masculinity that women crave.

This is what comes from living in an overly 'safe' and decadent society in a world concerned with 'conservation' and 'limited resources'. In times of war or 'open frontiers' men are encouraged to be more masculine. I think that this forced repression and taught self-loathing is a big cause of this trend. Other causes such as sexual assault from gay men also exist of course.