Evidence from earlier generations of adopted children (now adults) is that, at regular intervals through their childhood and well into adulthood, adopted people need to make sense of what has happened to them and why they have been placed for adoption. They need to know who they look like, whether they have any personality characteristics, talents or interests that they have inherited from their birth family. They often need to know medical information. Many talk about the need to know they were not forgotten, particularly by birth parents, siblings and grandparents.
Contact, whether it be by letter-box or face to face is a way of keeping this connection alive. This enables the child to ask questions of his adoptive family, and to have those questions answered when the child needs the answers, rather than having to wait until adulthood.