Have you ever wondered what good it does to have the top and bottom octave of your piano tuned? I’ve heard several people say, “Don’t bother tuning that those sections. Nobody ever plays those notes.” Although it maybe true that beginner and intermediate pianists don’t use the ends of the piano, there are still several reasons why it should be tuned.
First, pianos were designed to support several thousand pounds of pressure. If sections aren’t tuned, the unequal pull on the piano can cause the plate to warp. Although rare, this can ruin a piano.
Second, when the extremes of the piano are in tune, the strings will ring sympathetically with the notes that you do play giving your piano a much fuller, richer, and more pleasing sound.
(Information from Piano Technician Guild members and publications)