I don’t have kids and don’t want them. Like you I’ve also wondered about the question because I’ve never met someone who could directly answer your very basic question.

But I have been deciding if I want a dog recently and after reading through other replies I find the reasoning the same.

A dog is like a child that’s permanently stuck at 5.

They need to be fed and cleaned, they need to be walked multiple times a day and engaged with.

My cat who’s old has started meowing while standing next to the thing he wants recently. Food, hallway, balcony, fresh water, etc. he does this on a fairly predictable schedule.

I’m a person who’s schedule is rarely predictable (except for when I was younger and single and live a rolling 30 hour day).

I like having the cat, we’re best friends. But the part of having the cat be so needy is a nightmare for me. I haven’t had a good night’s sleep in months.

The meow he does now triggers some kind of paternal instinct in me that makes it impossible for me to just quickly finish my thought at work or whatever before getting up to serve him.

A dog would be even more needy because living in a big apartment they can’t get their exercise or bathroom needs met without me dropping everything to help them.

A child is even more needy, your sleep for several years is utterly destroyed, etc. and they tend to outlive you so the commitment is the longest of the three.

Your OP also doesn’t mention any of the horrific details of childbirth.

I’d never have kids for lots of reasons, the idea of putting my best friend through that horror makes it a nonstarter.

The real answer that people have kids are one or more of:
1. a mistake
2. their partner wants them so they go along with it
3. they’re convinced by social norms that they should
4. They have a basic drive to have children

Some of the people in the first 3 who didn’t have 4 may still have that drive kick in after they have kids. It didn’t happen for my parents but they’re malignant narcissists so it’s a different story.

Distilling what many other replies seem to be trying to express, in order to be a good parent you need stamina because so much of it is unpleasant.

The unpleasant parts can be rewarding or lead to personal growth so unpleasant may not be bad in of itself.

I’ve met people who join startups from FAANG and they’re overwhelmed with the demand and pace and they leave. And I’ve met people from all over who join startups and because the mission of what the startup is trying to achieve resonates with them as something bigger than themselves that will make the world a better place they embrace the pace and the need to go above and beyond.

I’ve been at startups where I didn’t sleep a lot because I was inspired or there was a critical deadline and needed to push something over the hill with the team to survive. Now later in my career I find it harder to get the same drive and satisfaction from that same sleep deprivation regardless of the reason.

People are blinded by the ambition, romance, comradely, accomplishing something difficult, etc. basically on an emotional level to overcome the turbulence of it.

If you’re looking to decide if you want to have kids or not, then not having some kind of drive makes it a gamble of whether you develop the drive after the fact or not. Without it there’s no set of clinical reasons that will make you choose to go through with it.

The idea that you have this choice is a privilege, many people have kids without it being a considered choice.