A. Ahhh, you are very perceptive! Interesting question you ask. First, let me address the first changes with the new translation we have which was implemented a couple of years ago and then address the recent addition by Pope Francis.
When the Liturgy was first translated into English (and other languages) this was the first time in the Church’s history that this was done. When the original translation took place in the early 1970’s the group entrusted with the translation, the International Commission on English in the Liturgy (or I.C.E.L), had to do this translation without any clear guidelines. Being the first time everyone involved in the translation no doubt did their best but, still, it was the first attempt. Furthermore, this first attempt at translating the Liturgy was done quite quickly.
Over the years there were many who began offering new suggestions and ideas for a better way to translate the Liturgy from the Latin. Pope John Paul II, in 1997, issued a document in which he set down some new guidelines on how to translate the Liturgy. Generally speaking he asked that translations be more exact rather than paraphrasing the Latin content. This started a long process of evaluating, study, conversation, consultation and re-translation which took many years. This time the Church wanted to truly set forth a translation that everyone agreed upon. Therefore, every bishop in the English speaking world was consulted as well as many scholars. They simply wanted to get it right. The result of this very long process is, what I believe, a very beautiful and very elevated English translation of the Mass. All of the hard work over many years paid off!
As for the recent change by Pope Francis this is something quite different. This was not a matter of determining the best way to translate the entire Liturgy, rather, it was the matter of expressing our devotion to St. Joseph in all Eucharistic Prayer rather than just one of them. You see, in 1870, Pope Pius IX proclaimed St. Joseph Patron of the Universal Church. The Vatican’s decree says that St. Joseph “stands as an exemplary model of the kindness and humility that the Christian faith raises to a great destiny, and demonstrates the ordinary and simple virtues necessary for men to be good and genuine followers of Christ.” In 1962 Pope John XXIII had his name inserted in the Roman Canon which is the first Eucharistic Prayer and the only one in use at that time. For some reason when the three additional Eucharistic Prayers were made available in 1970 they did not contain St. Joseph’s name like the Roman Canon did.
Apparently, Pope Benedict XVI had received many requests throughout the Church to insert St. Joseph into all the prayers just as Pope John XXIII did back in 1962 when he inserted his name into the only Eucharistic Prayer we used at that time. Pope Benedict XVI ultimately did approved of this right as he was stepping down as pope. However, Pope Francis quickly acted on Pope Benedict’s desire and made this a public decree. So, in a sense, you could say that this process started in 1962! Therefore it was a much longer process than the re-translation of the Liturgy which only began in 1997.