Why is the ancient form called the Extraordinary Form and not the newer form of the Mass?
The terms "ordinary" and "extraordinary" are more descriptive than prescriptive in Summorum Pontificum. The Holy Father notes in his Letter that the use of the old missal requires a certain amount of liturgical formation and knowledge of the Latin language. He goes on to say that neither of these are found very often. So, in the foreseeable future, the "Ordinary Form" of the Mass will refer to the use of the Mass most commonly said in Catholic churches throughout the world which is the Mass of 1970.