By leaving out the external characteristics, it allows the reader to formulate a personal picture of the character based on the reader's own perceptions and to allow the thought processes of the character to show through that imagined person and become more vivid and life-like to the reader.
I help out with our library's Friend's of the library's book sales. I help out with the Walk for Life annual garage sale. This year I assisted at the collection site for Christmas Boxes to be sent to children in other lands by the Franklin Graham association.