Raising children is just about the most exciting and challenging and rewarding thing that you can do in LIFE.
It's a great sadness for me that I never will. Many people these days have avoided getting children because the future of the world looks bleak and because of the economy. I've had coworkers who had (unplanned) children anyway, already fifteen-twenty years ago and
then lamented the state of the world that their children would grow up into. For me it is also that I don't want to pass on my cancer genes, and force the person I love the most to go through a similar type of hell to what I have.