Today much of the Tradosphere celebrates the issuance of then-Pope Benedict XVI's Summorum Pontificum, which largely deregulated use of the 1962 Roman rite. What is really used is not 1962, I do not think anyone uses 1962 by the book, but what I call the "Rite of Econe," the result of tinkering during the formative years of the FSSPX.
Early on, outside of France, most everyone in the traditionalist movement used pre-Pius XII. Even in France St. Nicolas du Chardonnet used pre-Pacelli until 1984 when the priest in charge of that church died. For some reason 1962 caught on in France. Why? Perhaps during the 1960s priests became gradually more agitated and stopped accepting changes at a certain point. Rather than turning back the clock they refused to go forward. This was the case of Fr. Quintin Montgomery-Wright, who then Sarum-ized the Roman liturgy and recovered the Norman liturgical heritage of northern France. It may also have appealed because of its very sparse and simple Divine Office.*
A man who was a postulant with the FSSPX in Econe "back in the day" once told me that they did 1965—essentially 1962 with the popular parts in vernacular and options for lay people to do readings—with some modifications, among them the Ordinary of Mass in Latin and the Confiteor prior to Communion. At some point they switched to 1962 outright at Econe, meaning all Latin, no lay readers, and recovering the hour of prime. They continued to make alterations—such as the epistle in French, bows to the Cross, and no genuflection for the Jews on Good Friday—until arriving at their current praxis. Do any readers, particularly older ones, know additional details about this development? After all the rite of Econe is the Extraordinary Form.
* = for example yesterday would have been Sunday and the Octave day of Ss. Peter & Paul, warranting nine readings at Mattins (including three from the superseded octave day being read as one long ninth lesson), commemorations at Lauds, Mass, and Vespers. This Wednesday would see Vespers of St. Elizabeth of Portugal followed by Vespers of the Dead, as the Officium Defunctorum is prayed on the first free day of the month in addition to the Office of the season/sanctoral cycle. Lent and Advent are especially involved in the old Office, with the Officium Defunctorum and Requiem Masses in additional to the Lent and Advent liturgy on Mondays. In 1962 Sundays usually have three lessons as opposed to the traditional nine. The difference could be up to 30 minutes of time in private recitation during violet seasons.