Well off the top of my head.....in any emergency/accident/lost child/stolen child/ hospital visit...involving police or other goverment or hospital personal etc.,with the bc and the photo there is no question you are the parents of the child.....without proof.......police or other goverment officals may want to hold you all until they are sure.....may not let you near your child in the hospital etc........
We never had to use them, but we also had the peace of mind that if needed the proof was with us and not in a drawer at home.
AKK