Why was doryphoros or spear bearer famous throughout the ancient world?

The Doryphoros (Greek Δορυφόρος Classical Greek Greek pronunciation: [dorypʰóros], "Spear-Bearer"; Latinised as Doryphorus) of Polykleitos is one of the best known Greek sculptures of classical antiquity, depicting a solidly-built, well-muscled standing warrior, originally bearing a spear balanced on his left shoulder.

The work nonetheless forms an important early example of both Classical Greek contrapposto and classical realism; as such, the iconic Doryphoros proved highly influential elsewhere in ancient art.