The issue is identity.
People crave identity and lineage through their parents.
It’s an instinctual emotion.
Many people who are deprived of this feel cheated of part or all of their identity ... many who are adopted feel this way and seek out their biological parents.
Society can try to make it taboo to have this natural instinct but they cannot erase it. They can only hound and bully those who speak out.
I so look forward to the day that these IVF kids start to sue the pants off their selfish whatevertheyare.
So far as I can tell, with several adoptions in my immediate family, this is not so much "natural instinct" as it is longing to fill holes in ones life.
The closest analogy I can think of is searching for "high school sweethearts" online when your marriage is in rough shape.
I don't disagree with D&G, but I also can't deny the efficacy of adoption as compared to biological parentage.