Today at the Angelus, Pope Benedict had something to say about the custom. As ever, it is thought-provoking and insightful, offering an original slant.
The Eucharist has a cosmic value: the transformation of bread and wine into the Body and Blood of Christ constitutes the principle of divinization of creation itself. That is why the feast of Corpus Domini is characterized particularly by the tradition of carrying the Most Blessed Sacrament in procession, an act that is rich in significance.(Translation by Teresa Benedetta of the Papa Ratzinger Forum.)
By carrying the Sacrament in the streets and in the squares, we wish to immerse the Bread that descended from heaven in the daily routine of our life. We want Jesus to walk where we walk, to live where we live.
On this day the Christian community proclaims that the Eucharist is for everyone - it is life itself, the spring of life which conquers death. From our communion with Christ the Eucharist, comes that love which transforms our existence and supports our journey towards our heavenly Home.