When they have absolutely zero interest in family life? I see it on here constantly. I don't mean men who accidentally get someone pregnant and shirk responsibility... I mean men who enter into a relationship with a woman, propose, get married and try for babies... then end up with two toddlers and a presumption that they can dump everything onto the wife and fuck off out all weekend every weekend to play golf? Or get smashed in the pub? Or sit playing video games all day? I myself loathe the thought of family life - I just wouldn't want to be tied to anyone and would feel suffocated and resentful. So why on earth don't they just stay single and childless?! Baffles me.
(Disclaimer - I know there are loads of really good men out there!)