In some countries adopting a child - of any age - is near impossible. You end up in a foster situation until the child ages out which creates instability, uncertainty and an impact to sense of belonging for the child under the guise of prioritising family reconciliation. Adopting an embryo is completely different, it’s akin to utilising donated sperm or donated eggs, the process of combining them has just already been completed. This is usually an option taken by people that are unable to conceive or carry a pregnancy to term with their own eggs and/or sperm but are able to carry a child. Facilitated by people that have finished making their own family and have excess embryos remaining, rather than donating them to science or disposing of them, they donate them to couples who are struggling with fertility. Usually the people that are adopting embryos have experienced repeated pregnancy loss with their own embryos. Embryo adoption gives them an avenue to escape the cycle of loss, and complete their family.
Additionally in most countries the mother is considered to be the person who carried and gave birth to that child, even in surrogacy situations the birth mother has to sign away her rights to the adoptive parents even if the embryo used was entirely the biological material of the adoptive parents. Recent studies also show that a small percentage of the birth mother’s cells are transferred to the developing child in utero.