We use the appellation Sri for denoting sacredness to all things which need to be sanctified. The appellation of Sri is affixed to human bodies which are temporary and made up of five material elements to denote our respect. We also use this appellation even in the case of the Lord because the body in which he appears is temporary. In the case of Rama or Krishna, we use Sri because the names refer to the bodies which were impermanent. Thus, for giving sacredness to a destructible body, we use Sri.