Scared is an adjective used to specify fear and anxiety. A person who is scared is often anxious or frightened about something. The word afraid is used to express some emotion or being filled with fear.
The word "scared" sounds like a childish emotion, and it conjures up imaginings of a child being fearful of the dark, or so scared that he or she must sleep with light. The word afraid is also used to express compunction, apprehension, or reluctance. The word scared does not fit these descriptions.