I see it the same way as people who have iPhones or luxury German cars.
People who have iPhones or luxury German cars are more likely than not to rate themselves as satisfied with their purchase.
It is as simple as wanting to feel good and usually it feels good to believe I am correct.
Therefore, I suspect this is correct for both breeders and the child free
that we will try to justify our own decisions,
not for anyone else but to satisfy ourselves.
We probably get simply defensive when questioned.
It may not have anything to do with the greater fool theory as we aren't constantly buying or selling children or doing child swaps like banks do with money but it is worth bringing up as we are humans in both places and I suspect the underlying human psychology is the same.
> In finance, the greater fool theory suggests that one can sometimes make money through the purchase of overvalued assets — items with a purchase price drastically exceeding the intrinsic value — if those assets can later be resold at an even higher price.
> In this context, one "fool" might pay for an overpriced asset, hoping that he can sell it to an even "greater fool" and make a profit. This only works as long as there are enough new "greater fools" willing to pay higher and higher prices for the asset. Eventually, investors can no longer deny that the price is out of touch with reality, at which point a sell-off can cause the price to drop significantly until it is closer to its fair value, which in some cases could be zero.[1][2][3][4]
https://en.wikipedia.org/wiki/Greater_fool_theory
tl;Dr NEVER EVER trust a parent to tell you the truth about the "wonders" of being a parent, not because they are malicious but because they are likely incapable of being objective.
edit: disclaimer, if it wasn't obvious, i made this all up. i don't have any children