A beautiful smile is attractive on a 75 year old and on a 12 year old. It is timeless. It does not change with fads or fashion. No matter what you are (or aren't) wearing, no matter what your hairstyle (or lack thereof), no matter what time of the day or night, you can always have that beautiful smile!
When a person is unable to smile confidently, MUCH is lost.
Communication of the person's best feelings is stifled. Highs and lows are part of the reality of life. Not being able to fully experience and share the highs with others is a sad situation to be in, and takes away from some of the finest experiences life has to offer.