Perhaps I can clarify, at least somewhat, why some of us are childless.
Some people feel dedicated to a calling other than being a parent. Often times this calling actually stands in the way of being a good parent.
Some people have serious medical or psychological issues that they don't want to pass on to their children.
Some people just don't feel the "need". Sure, they might "learn to love it" when they jump into parenthood, but that's too big a risk to take when creating an innocent human life.
Some people have serious personal problems and they realize they would make terrible parents, even if they wanted and loved their child.
And a lot of these people don't scorn parents and don't hate children. They simply don't see parenthood as the path in life they are meant to take.
Personally, I don't think these people are immature or somehow "less human" than others.
I have no problem with people who choose not to have children for any reason. Just like no one has to understand why I enjoy kids so much and how being a mom is and always was the most important thing to me. I would have liked to have 10 (that scared the hell out of some boyfriends, lol) but stopped at 4.
You made some excellent points in your post.