I don't have anything against those who choose not to have children. In a lot of ways, it's probably for the best.
I think that some parents who are able to have their own children take the process for granted, and they don't understand the undertaking and what it really means to raise a child. My wife can't have children, so imagine her being around her friends who practically shoot them out at will, and then have the gall to complain about their pregnancies and their kids around her. Talk about selfish.
But not having children right away was a wonderful opportunity for us to observe others. And we took it seriously. We watched a rather large selection of our friends and family go through the trails and tribulations of child-rearing and saw all the things that worked and didn't work. We asked questions of couples we knew that had kids that grew up well. So when the time came for us, we had at least a plan of attack.
I never wanted a lot of children, even had we been able. I was happy with one. I am glad that we adopted because I am adopted and I know what it meant to me. The process was long and hard, and I think that every single person about to think about parenting should have to go through it, if for nothing else than to test their committment to having a child.
I think it's a personal decision based on your lifestyle. And I don't think any decision starts out as a bad one when deciding on children as long as it's a responsible one that was a conscious decision. It's what you do once you have them.