Sections 134-141 address the second concern of Chapter VI, “Certain Forms of Worship of the Most Holy Eucharist Outside Mass.”
I confess the wane of Eucharistic devotion is a curiosity to me. It must have meant something more than “something Catholic we must do” before Vatican II. On the other hand, if it did, I don’t think the good urge to counteract the cease rush of modern life would have faded from Catholic consciousness.
That said, it’s been a part of the devotional life of every Catholic parish I’ve served in the past 25 years. I suspect there is some connectiono between taking liturgy seriously and taking prayer seriously. The CDWDS gives a lot of traditional reasons for doing it:
[134.] “The worship of the Eucharist outside the Sacrifice of the Mass is a tribute of inestimable value in the life of the Church. Such worship is closely linked to the celebration of the Eucharistic Sacrifice.” [Ecclesia de Eucharistia 25] Therefore both public and private devotion to the Most Holy Eucharist even outside Mass should be vigorously promoted, for by means of it the faithful give adoration to Christ, truly and really present, [Cf. Ecumenical Council of Trent, Sessio XIII, 11 October 1551, Decree on the Most Holy Eucharist, Chapter 5: DS 1643; Pius XII Mediator Dei; Mysterium Fidei; Eucharisticum mysterium 3f; Inaestimabile donum 20; Ecclesia de Eucharistia 25] the “High Priest of the good things to come” [Cf. Heb 9:11; Ecclesia de Eucharistia 3] and Redeemer of the whole world. “It is the responsibility of sacred Pastors, even by the witness of their life, to support the practice of Eucharistic worship and especially exposition of the Most Holy Sacrament, as well as prayer of adoration before Christ present under the eucharistic species.” [Ecclesia de Eucharistia 25]
[135.] The faithful “should not omit making visits during the day to the Most Holy Sacrament, as a proof of gratitude, a pledge of love, and a debt of the adoration due to Christ the Lord who is present in it.” [Mysterium fidei] For the contemplation of Jesus present in the Most Holy Sacrament, as a communion of desire, powerfully joins the faithful to Christ, as is splendidly evident in the example of so many Saints. [Cf. Ecclesia de Eucharistia 25] ‘Unless there is a grave reason to the contrary, a church in which the Most Holy Eucharist is reserved should be open to the faithful for at least some hours each day, so that they can spend time in prayer before the Most Holy Sacrament.” [Code of Canon Law 937]
[136.] The Ordinary should diligently foster Eucharistic adoration, whether brief or prolonged or almost continuous, with the participation of the people. For in recent years in so many places “adoration of the Most Holy Sacrament is also an important daily practice and becomes an inexhaustible source of holiness”, although there are also places “where there is evident almost a total lack of regard for worship in the form of eucharistic adoration.” [Ecclesia de Eucharistia 10]
.. but frankly, the way in must involve something of the practical value of wasting time with the Lord. Perhaps it is not the best motivation to tell people what’s in it “for them,” but in a culture steeped in rationalism, productivity, and doing things, sometimes people need permission to be imaginative not reasonable, receptive not productive, and being a Catholic and not just doing Catholic things.
My sense is that the desire for contemplation never went away–it is part of the human condition. Some clergy and lay leaders have never tapped into this. And maybe that “never” was part of the preconciliar experience as well.