By isolating the other family members from the truth, it assumes that they are incapable of dealing with the problem. When others note a change in behavior, they often will attempt to determine what is causing the change. Their imaginations will work overtime, and will create alternatives which are even more serious than the real situation. When children or adults are entrusted with the real situation, they can help contribute to minimizing the negative effects of the change. This allows each family member to be an active member of the family, for better and for worse.
Most family members appreciate the opportunity to understand the real concerns within the family.
It also allows them the potential for helping seek alternatives which can help deal with the problem at hand.