The key to seeing why there should be a Eucharistic worship distinct from the Mass is that the Eucharist is Jesus Christ. No less than His contemporaries in Palestine adored and implored Him for the favors they needed, so we should praise, thank Him, and implore Him for what we need.
Pope Pius XIIBeyond fashion and its demands, there are higher and more pressing laws, principles superior to fashion, and unchangeable, which under no circumstances can be sacrificed to the whim of pleasure or fancy, and before which must bow the fleeting omnipotence of fashion. These principles have been proclaimed by God, by the Church, by the Saints, by reason, by Christian morality.
Pope Pius XIIJust as the divine Redeemer, dying on the Cross, offered Himself as Head of the whole human race to the eternal Father, so also in this "clean oblation" (Mal 1:2), He, as Head of the Church, offers not only Himself but, in Himself, all His mystical members.
Pope Pius XIIThis practice of adoration is based on strong and solid reasons. For the Eucharist is at once a sacrifice and a sacrament; but it differs from the other sacraments in that it not only produces grace, but contains in a permanent manner the Author of Grace Himself. When, therefore, the Church bids us to adore Christ hidden behind the Eucharistic veils and to pray to Him for spiritual and temporal favors, of which we ever stand in need, she manifests faith in her divine Spouse who is present beneath these veils, she professes her gratitude to Him, and she enjoys the intimacy of His friendship
Pope Pius XII