This sentiment that it's nearly impossible to convey the meaning it provides is always irritating to hear. It's an extremely condescending idea to have, when the meaning it gives people is pretty obvious to see in siblings and friends/coworkers who do have children. But that's just more reason to want to wait until you feel ready to take on the job.

I've seen how my sibling changed upon starting a family, I've seen how my PhD advisor proudly talks about every little thing his kids do.

The value it gives them is obvious, but that's just more reason not to irresponsibly pop put a baby when I barely make enough to support myself, when I don't know if I'll stay in the country I'm in, when I've had very little time being mature enough to know if my partner is someone with whom I can expect to provide a good environment for at least 18 years.