Many millenials witnessed their parents divorces or raising kids never married and don’t want to go through it OR have kids and put them through it. Rather than strengthening marriages and learning social skills, they opt out with a socially acceptable alternative to children - pets.
My wife and I sure did. It instilled a 'don't let this happen to YOUR family' attitude within us, so we give OUR children that which we never had. Hell, I lost count of how many times my mother has been married now. I think she's always on the lookout for a future ex-husband. I have nothing to do with her. She's a loser - Another thing I learned is that it's never good to closely associate with losers, unless you want to lose along with them(I don't care if I happen to be related to them). Nothing good ever comes out of hanging around bad people. We try to instill those concepts within our children as well - I don't care if it results in them being snobbish assholes or without any "friends". I think they'll be better for it in the long run.