Also, you said do not usually appear in life without having children, so what are the scenarios where hey appear without having children? Wouldn’t that imply events that a non-parent could draw parallels from?
No, that would imply that not everyone who has those kinds of experiences is neccessarily a parent. There are many aunts, uncles, brothers, sisters, whatever who raise kids in a parent-like fashion or help out significantly in the upbringing of those children that they'd have the same emotional experiences as parents. That does not go for childcare workers who have a different relationship to the kids. It's just something completely different if you are responsible for organizing and structuring and executing a daily life.
Being a parent is not a job, it’s an event that happens.
What?! Like... just... what?! Yeah, sure... my work as a father was done at birth, parenting being a one time event and all. I gave my son a stern talking to about the meaning of life while the pediatrician examined him right after birth and that should have been that... right? May I ask how old you are? Have you the slightest grasp what the daily life of a parent looks like?! What the hell?!
It is not the only route to key insights into the human mind and psyche.
Of course not. It is just (almost, see above) the only way to unlock the mindset of a parent. That's not the only perspective life holds by any means, just one that cannot (and should not) be assumed one can relate to whithout any personal experience. Just as one who has never had to fear for their life assume that they know what being in a warzone and being shot at feels like. You wouldn't give a soldier tips on how to handle their experiences without being asked, would you? Why is it okay to judge parents then?
Don’t be so limiting on your fellow members of humanity just because you have this bias that parenting Is the only way to this special subset of knowledge.
It is though. Just as fearing for your life is the only way to experience how that feels, or just as falling in love is the only way to experience how that is like.
Imagine someone who's never fallen in love or been in a relationship. No imagine that you have freshly fallen in love and had to go on a business trip with that person. While your hormones run amok and you experience physical pain from missing your new love just so much, imagine the other person lecturing you on how you should deal with the feeling and how you should go about the new relationship while judging you for the way you want to go about it because he is oh so sure he knows what's up. Wouldn't that kind of piss yo uoff?