Because we have to follow the Roman Missal exactly. The words are “The Body of Christ” and we cannot change that on our own.
It isn’t that the words themselves are somehow wrong. The words for Communion are different in the Ordinary and Extraordinary Forms. Neither is right or wrong, and there are perhaps other forms that might be just as appropriate, maybe even ones that no one has yet composed. Yet, we must always follow the text of the Mass as the Church has given it to us.
Since the only option in the Missal (Ordinary Form) is to say exactly the words “The Body of Christ” then, that is what we must do. Anything else, any other change in the words, would be presumptuous. We can make suggestions (through various channels) that the Church change the text, but to do that on our own is an abuse.
The practice in the Eastern Churches is to call the Communicant by name; at least “most” of the time. The Eastern rubrics don’t operate quite the same way that the Roman ones do. Most of the time, a name “should” be used, but if the priest doesn’t know everyone’s name, well, then he just can’t (unless the deacon helps him). The point is that when we see it done this way in the Eastern Liturgies, it’s perfectly legitimate. It just illustrates the fact that there is no one “right” way to do it, but that decision is not something to be made by the local priest, deacon, or EMHC, and not even the local bishop. In order for another form to be used, that form would first need approval from Rome.
