A piece can look good and need refinishing, or look bad, and a touch-up & clear-coat will restore it. The purpose of a finish is to protect the wood from moisture changes that can destroy the piece. To refinish or touch-up? An easy way to tell is the thumbnail test. Simply try scratching the surface finish with your thumbnail where it won't be noticed (a corner or edge will do). If the finish is aged or soft, it will mark or flake off easily. Just as you would not paint over old flaking house paint, a touch-up and clear coat will not work over an old soft finish; refinishing will be required to give the wood the protection it needs