Yet the offertory antiphon is not in the missal. So it is almost never used, because you must go to another book to find it, and that book is not in the vernacular. Singing it is a
different issue. A priest may chant whatever is in the missal, but properly speaking the sung antiphons are to be taken from the Graduale Romanum. Yet, the introit and communion antiphons are in the missal in the vernacular, so those end up being used, usually said, as intended.
Father, let me clear up some things.
The propers in the Missal are often/usually not the same as the ones in the Graduale. They are different texts. The propers in the Missal are to be used only when the Mass is spoken, like at a weekday Mass. The propers in the Graduale are used only when they will be sung.
Propers in Missal=recited
Propers in Graduale=sung
If you notice in the EF, the propers in that Missal align perfectly with what is in the Graduale. But when the “reformed” Missal came out, the Consilium decided that they were going to keep the Graduale propers but also, in the Missal, have a different set of shorter propers. They thought it was silly or something to have to receite the whole Introit with its Psalm and Gloria Patri at the beginning of Mass, so took some short Bible quotes and put them in the Missal for
only the Introit and Communion.
The reason that none of the Masses have Offertory antiphons in the OF Missal is because they thought it messed up the “flow” of the Mass at that part or something, so they made a strategic decision, for better or poorer, to leave it out.
The fact that none of the Masses in the Missal have Offertorys has nothing to do with sung Masses; the antiphons in the Missal were only ever intended for recited Masses in the first place.
So what we end up with is this fantastically confusing historical situation in this thread with you and I going back and forth on this point. =p