Is there an un-selfish reason to produce your own offspring to raise as opposed to adopting someone else's? The positives I find in parenthood lead me to clearly choose adoption over having my own children, although the genetic bond is a tough one to overcome: usually the argument for having children is that it comes from and is a symbol of intimacy between the parents, and that the similarities stemming from genetics (whatever they are) make for a more enjoyable family. For the child, too, not just the parents, I mean. I'm not sure how much of an excuse that is.
Is there a common incentive for people to have children, knowing that they will give them up for adoption?