For what it is worth, we Catholics do not believe it is a power of the priest that does this. It is Jesus doing it through the actions of the priest. Similarly, when a priest pronounces absolution after a person confesses his sins, its not the priest forgiving our sins, it is Jesus. This is done because we humans are physical beings as well as spiritual, and its good to have those sensory cues, like the priest pronouncing the words of consecration, and the words of absolution. It is so much more comforting to actually hear those words of forgiveness than to just assume them. This is also why we Catholics have the "smells and bells" in our liturgy. Our physical senses are to be used to experience the sacred.