Sorry, but in many cases *having* children is a selfish act. It is fulfilling the wants or needs of the parent. I don't know any one who says "You know, I really detest children but I'm going to make them and raise them anyway for God and Country." Every single person I know who planned for their child wanted children. They wanted a family. They wanted parenthood experiences, wanted to raise a child. That's fine. However, I don't buy that it is some noble act to reproduce. All species want very badly for their kind to carry on--it is hardwired into arguably most humans to make more humans at some point. Do parents make sacrifices? Sure--my mother made incredible sacrifices for me that I am thankful for everyday--but she raised that this is nothing noble, but simply expected if you are going to have children.
DH and I have not decided about kids yet. And the reasons do start with I. As in, I was raised that your child is your first priority, and if you are not ready to make it such, you should not have a child. I have have mental and physical health issues that I need to get a handle on before I bring another little being into the equation. I am not entirely certain that I would make a great parent.
If we do decide to have kids, it will be be we took our time and thought it through carefully and decided that it was really want we wanted to do with our lives, not because we deluded ourselves into believing that somehow society will just not survive without our genes in the pool.
It irritates me when people who have kids insist on trying to "sell" the idea of children on everyone who does not. I think it's fantastic if you have kids and love them, and your kids are lucky to have such adoring parents. However, people should NEVER feel pressured into such a life changing decision, and if they don't want kids, it's not any of anyone else's business. I love dogs and my life has been enhanced by owning them. I love being married to my husband and he is my best friend. However, I don't run around telling everyone who is single or dogless what they are missing all the time.