@Kagekokoro @dave
You get more attached to the newborn baby, than if you were to adopt a 2-3 year old. Also, I'm assuming that it has part of the DNA of one of the couple, so that gives a bit more incentive to care for the kid.
It's shitty to be able to recognize this, but objectively there are more reasons why someone should invest more care in a surrogate child than an adopted one.