Well, a topic in the minds of many people. Why have children indeed? Well, the answers posted here range from heartwarming to disturbing to very bleak indeed.
I can't give any testimony to the merits of parenthood in a subjective sense as I am yet to be blessed in that area (if it happens at all). But I would like to give a couple of arguments from a purely observational stance.
Firstly, you ask what it is that makes having children worth the pain they will suffer. Well, what's the alternative? The extinction of the species? You have to ask yourself the question, is our species worth sustaining? Personally I think it is. Granted we are heavily flawed. We are also, however, unique in all the universe (or so I would suppose
). Are the merits of our species and the legacy we would pass on worth the trials one must face to live a human life? There are many things worth suffering for, I think our future is one of them.
Secondly, why do we have children? That is, why does one person (or rather two
) choose to be the one to bring a child into the world. True there is the biological drive, a strong factor, yet reasoning people are able to deny such urges when they find them inappropriate. You could say preservation of one's own genetic code. People have a tendency to contemplate their own mortality, reproduction allows a part of you to continue in the living world long after your own demise. Call it a search for immortality.
Anyway, I don't know if this has helped you find a satisfactory answer. All I know for sure is that babies are absolutely adorable and I hope like hell that when and if I have one I'll be able to load the scales of it's life with more joy than sorrow.