A man used to be undressed without a knife in his belt. Literally you did not leave home without a sharp bit of metal in case you had to stick it into another human being, typically because they were trying to do the same to you.
Remember Romeo and Juliet? The Mont. and the Cap. boys were not lower class yobs. Fighting in the street with freaking swords was their golf.
- - - -
One of the unspoken fears that we men have is the knowledge that the women and children don't really need us. They like us and love us but they don't need us. Not in a civilized "Star Trek" world, which is the sane result that we are all striving for (right? right?).
With modern technology they don't even need us to reproduce.
In the extreme (usually only talked about in Sci-Fi and hyper-feminist manifestos) men are a luxury or a fetish.
(In case it's not clear, I'm putting this out there for the sake of stimulating discussion. I'm not a man-hater on anything like that. Heck I am a man, and I like being one. However, the point above still stands: once you break down traditional marriage in a technological society, men are not necessary.)