The Holy See's reason for allowing this Indult to expire is that the purification of the vessels is by right a function of the clergy and therefore is relegated to the priest, deacon (or in places that have them) an instituted acolyte. It is not required that this be done during Mass. It is perfectly acceptable that the vessels be purified after Mass in the sacristy.
The reason I'm bring this up is that I attended a conference recently where the revocation of the Indult and enforcement of the standing practice was referred to as the action of "isolated bureaucrats in Rome who are out of touch with the real world because there is a priest behind every pillar in Rome." The idea being that all Masses in Rome are concelebrations with lots of priest present to do the purification of the vessels. The lack of theological understanding in the statement is staggering.
Even more recently I was discussing the habits of a particular visiting priest who both broke the host during the consecration and turned over the purification of the vessels to the EMCs. He was from outside the U.S. so I don't know if these are norms in his country of origin or just bad practices on his part. But in the discussion one of the other participants stated, "Yeah he let us do the dishes, that's how it should be anyway, after all we're priests too"
As in the above statement the complete lack of theological basis for such a statement is fairly staggering. The sacred vessels which hold the Blood of the Savior referred to as equivalent to dinnerware and the act of purification, based in the priestly office, relegated to starting the dishwasher shows a lack of real appreciation of what is happening at the alter.
As is required by the General Instruction of the Roman Missal:
All, therefore, whether they are ordained ministers or lay Christian faithful, in fulfilling their office or their duty should carry out solely but completely that which pertains to them.This is pretty clear. Purification of the Vessels is a duty of the ordained ministers. It is a abuse for a member of the lay Christian faithful to carry out that duty.
As it says in Redemptionis Sacramentum:
The Priest, once he has returned to the altar after the distribution of Communion, standing at the altar or at the credence table, purifies the paten or ciborium over the chalice, then purifies the chalice in accordance with the prescriptions of the Missal and wipes the chalice with the purificator. Where a Deacon is present, he returns with the Priest to the altar and purifies the vessels. It is permissible, however, especially if there are several vessels to be purified, to leave them, covered as may be appropriate, on a corporal on the altar or on the credence table, and for them to be purified by the Priest or Deacon immediately after Mass once the people have been dismissed. Moreover a duly instituted acolyte assists the Priest or Deacon in purifying and arranging the sacred vessels either at the altar or the credence table. In the absence of a Deacon, a duly instituted acolyte carries the sacred vessels to the credence table and there purifies, wipes and arranges them in the usual way.The source for this is the Roman Missal:
163. Upon returning to the altar, the priest collects any fragments that may remain. Then, standing at the altar or at the credence table, he purifies the paten or ciborium over the chalice then purifies the chalice, saying quietly, Quod ore sumpsimus (Lord, may I receive), and dries the chalice with a purificator. If the vessels are purified at the altar, they are carried to the credence table by a minister. Nevertheless, it is also permitted, especially if there are several vessels to be purified, to leave them suitably covered on a corporal, either at the altar or at the credence table, and to purify them immediately after Mass following the dismissal of the people.The requirements are extremely clear. They were set when the Ordinary form of the Rite was established and are not the result of some recent bureaucratic decision. Anyone who supposes that is misinformed of the facts.
193. When the distribution of Communion is completed, the deacon returns to the altar with the priest and collects the fragments, if any remain, and then carries the chalice and other sacred vessels to the credence table, where he purifies them and arranges them in the usual way while the priest returns to the chair. It is also permissible to leave the vessels that need to be purified, suitably covered, at the credence table on a corporal and to purify them immediately after Mass following the dismissal of the people.
192. Likewise, when the distribution of Communion is completed, a duly instituted acolyte helps the priest or deacon to purify and arrange the sacred vessels. When no deacon is present, a duly instituted acolyte carries the sacred vessels to the credence table and there purifies, wipes, and arranges them in the usual way.