Actually, if you work with young people who have spent most of their lives in "the system" you discover that many of them experience significant delays in development. They are all over the map due to trauma and constant disruption of their growing up years. Ironically, these kids are expected to be adults at 18 when they are often functioning as young adolescents in many areas of their lives. Adoption also provides legal kinship--parents, grandparents, other siblings, aunts, uncles, cousins. This is significant in terms of both medical emergencies and inheritance rights. There are many good reasons for a young adult to be legally adopted by a family if they have none of their own.