There's a shortage of babies thanks to abortion on demand. The red tape involved to be approved for adoption can be prohibitive too. There's more than one reason that they may have chosen this path. We really don't know.
Also a lot of couples are afraid of getting attached to a child only to have the biological parents change their minds a few years later and the courts siding with the biological family.
Notice I said "children" not babies. It is ego that demands babies, compassion that says any child.
Ego that says I don't want to take a chance on attachment and loss. It's all about me, my wants, my desires, my fantasy of the perfect life, the perfect child.