Ancient art is of twofold significance, as implied by the name. When an object is ancient its importance comes from the mere fact that it is an example of something that no longer exists, or something that teaches us about ITS culture or civilization. This is true even of objects that were not created as works of art but as artifacts, such as ancient tools or eating utensils.
But when an object is not only ancient, but is also considered an art object, either when it was created, such as a sculpture or paintings, or in the present day, such as coins or pottery, the object takes on a significance much more meaningful than the mere fact that the object is old.