Usually those who say to stay out of relationships, not get married, and not have kids, are those who picked the wrong woman or suck themselves.
Right, if you are dysfunctional in maintain a relationship with women or are so self-absorbed that you suck at raising kids, then don't have them! The rest just bitch because they got unlucky with a basket case woman or thought they would get their precious beauty sleep and not have their individual joys not infringed upon--kind of like still living single--when they had kids. So they tell everyone else not to.
Then if one to profess that they actually love their wife, in-laws, and kids and enjoy being married there are the old and tired cliches for them, "You'll see: you're kids are gonna hate you and your wife is gonna cheat on you. How ya gonna save money? They're so expensive."