No, I am referring to the modern names (that you find in the RSV or NRSV). Using the Latin names, they were called 3 Esdras and 4 Esdras.
And I might point out that you can ask the same question about Catholic Bibles – why do they omit these works and the Prayer of Manasseh, which were all in the Clementine Apocrypha?
And while it is true that the Council of Damasus (again, we are not certain because we have no original reports from this Council) probably did affirm the same canon as we have today, that decision was reversed six years later, when the Council of Hippo dropped Lamentations from the Canon – showing the canon was in flux.
By the time of the Council of Carthage (397), the list had changed again – according to Canon 26 of that Council, Lamentations is out, and there is a reference to 1-5 Solomon (which probably means – but we are not sure – Proverbs, Ecclesiastes, Songs, Sirach, and Wisdom.)
The Council of Damasus did definitely set the New Testament canon. However, the Old Testament Canon was not definitively set until Trent.
Finally, I will add that the theologians I listed are not just any ordinary theologians. For example, Gregory the Great was pope, and if the Canon had been definitively set, it seems unlikely that he would have disputed it. (However, in fairness, I must point out that his opinions were personal, and not magisterial in this regard.)