"My dog is a bit of a baby substitute its not the same as a baby but it's very satisfying to that need for something to look after and love. I'm not saying a dog can replace a baby, but it does bring a lot of joy to my life and I feel taking good care of the dog is worthwhile in a small way"
"Are we just ignoring this insanity? Probably for the best."
I am childless and have dogs. I don't consider dogs to be 'baby substitutes', but I wanted to respond to the 'insanity' comment here because for me, caring for animals has been one of the things that's given my life purpose and brought me a lot of joy (as well as heartbreak), and probably the main thing that's helped me cope.
Our dogs have all been rescues, either on a foster or permanent basis, some of whom would have been put down or spent the rest of their lives in a kennel otherwise. And not having children has meant we could take in the difficult-to-home ones, the strays with unknown backgrounds, the ones with a few months to live, the nervous, abused ones, who wouldn't have been able to go to a home with children. I've started to be able to see our child-free home as a blessing, a sanctuary not an empty shell.
With my last dog, who we sadly lost earlier in the year (an abuse case who never entirely trusted anyone but me), I remember one occasion being in the park on a nice day, with lots of families and children playing, which normally would have been difficult for me. I remember getting down to put his lead on, and give him a bit of reassurance amid all the commotion, and him just looking into my eyes with that steady, trusting look that he never gave to anyone but me, and giving my face a little lick. And in that moment I remember thinking, suddenly, clearly, 'I wouldn't swap you for all the children in the world'. And it was true, and still is. It's still painful at times, but since that moment I've felt a genuine peace with and acceptance of my childlessness.
Maybe that's 'insanity' (quite possible as actually mental health-related issues are among the reasons I haven't been able to have children), but the OP asked how people cope, and, for me, this is how.