This was part of the decree
Cum Nostra in 1955 by Ven. Pius XII., which reformed the kalendar and made slight modifications to the rubrics. A commentary by renowned liturgical expect J.B. O"Connell, “Simplifying the Rubrics” (London: Burns & Pates, 1955) states the following:
"A vigil may be defined as the liturgical (by an Office and Mass) and ascetical (by a fast) anticipation and preparation for, the greater solemnities of the Christian year. Originally, a vigil was a night service of psalms, hymns and prayers on the eve of a solemnity, terminating in the celebration of Mass after midnight. It took place on all Sundays, of Quarter Tense Days, and the greatest of all feasts, Easter, and (later, at least from the fourth century), Pentecost. Later there was a vigil also for the feasts of the more illustrious martyrs. At first the vigil (the night watch) was just part of the festal celebration of a solemnity, and partook of its joyful character. But from about the fifth century, the practice began to grown of preparing for the greater festivals by a time of special prayer and penance. Accordingly, the vigil began to acquire a penitential character, with a fast attached to it, to assume s separate existence (finally with its own Office and Mass), and to be celebrated more and more before the feast itself, at first on the preceding evening, then in the afternoon, and finally it arrived at the morning hours of the preceding day (by the fourteenth century). Then came the period of the vigil’s decline, the growth of the number of feasts began to deprive it of its own Mass and Office, reducing it to a mere commemoration, and the penitential part (the fast) grew less and less. And so, today, of the fourteen common vigils, six are commemorated only–being displaced by feasts of the double rite–and one being moveable (the vigil of the Ascension) is often so displaced. The Code of Canon Law fixed the fasting vigils as those of Pentecost, the Assumption, All Saints, and Christmas; and after the war, these were reduced to two, the vigils of Assumption and Christmas. All this means that the celebration of vigils is now but a mere shadow of its former self.
"The new rubrics leave intact the two privileged vigils of the first class (the vigils of Christmas and Pentecost, and this latter has been raised to a double rite), abolish the only privileged vigil of the second class (that of the Epiphany, given this rank in the Pian reform to give it a liturgical standing equivalent to a Sunday) and leave only five common vigils.
"Commentary: Hitherto SS. Peter and Paul (28 June), S. Andrew (29 Nov)and SS. Simon and Jude (27 Oct) had a vigil with a proper Mass; S. James the Greater (24 July) and S. Thomas (20 Dec), a full vigil with the Mass from the Common; the vigils of St. Matthias (23 Feb), S. Bartholomew (23 Aug), and S. Matthew (20 Sept) were commemorated only and that from the Common of a Vigil of Apostles; while S. John (27 Dec), and SS Philip and James the Lesser (1 May), had no vigil. Of these vigils of an apostle, only one remains now, that of SS. Peter and Paul, commemorated. In addition, the vigils of the Immaculate Conception (7 Dec) and of All Saints (31 Oct) have been abolished. In other words, one privileged vigil and nine common ones have been suppressed. The only feasts henceforth that have Octaves (Christmas and Pentecost) have retained their privileged vigils; the third, greatest solemnity of all, Easter has–with its own octave–a vigil that is now merged with the feast itself.
"Of the five common vigils that have been retained, that of the Ascension has been kept for practical convenience. It has three lessons forming a homily on the gospel that is proper to the vigil, if this were suppressed, there would be no lessons–until the texts of the Breviary have been reformed–to replace those proper to the vigil.
“The other four common vigils remain, because they are the oldest ones in the Proper of Saints, and even though only two of them can be celebrated fully, the other two (the vigils of SS. Peter and Paul, and S. Lawrence), being displaced by two feasts of double rite. This anomaly will, probably, be correct6ed in a future reform of the kalendar.”
Thus, the suppression was apparently part of the series of liturgical reforms aimed to trim the kalendar of accretions that had accumulated over the centuries.
