With the whole, put up for adoption option, I don't think it's about doing that so you can give a baby to someone else at all. It's more another option for the baby, rather than terminating it, deciding to carry it and give it life and then find another family who want to care for it. Though I really don't know how many women could do that, would be incredibly hard.
It's not about having babies for those who can't, it's just another alternative to ending the babies' life. Well that's how i see it anyway. I guess it's about doing a selfless thing for the baby, not to make a childless person happy.