The OP somewhat hinted at it in his question: lots of people's lives are made worse by having kids, but they wouldn't be able to live life if they accepted that reality. Society would shame them, their family would shame them, their children would be hurt, and they would have to live life knowing they made a mistake. It's easier to believe that it's 100% a good thing without any downsides and everybody should do it. The giveaway is not that they say everyone should try it (which also applies to cats, travel, etc), the giveaway is when they say nobody would be better without kids. That's a ridiculously improbable claim, but it's the basis for most people who say everyone should do it