A logical and appropriate corollary of the principle that people should do the things proper to their office, and only those things:
[45.] To be avoided is the danger of obscuring the complementary relationship between the action of clerics and that of laypersons, in such a way that the ministry of laypersons undergoes what might be called a certain “clericalization”, while the sacred ministers inappropriately assume those things that are proper to the life and activity of the lay faithful. [Cf. Pope John Paul II, Allocution to the Conference of Bishops of the Antilles, 7 May 2002, n. 2; Christifideles Laici 23; Ecclesiae de mysterio 4]
Often there is an impulse on the part of well-intentioned Catholics–clergy and laity alike–to do something more competently than someone else. My sense is that this is less often “clericalization” and more something along the spectrum of “busybody” to “incompetence.” Maybe with an occasional dash of laziness on the part of the one usurped.
[46.] The lay Christian faithful called to give assistance at liturgical celebrations should be well instructed and must be those whose Christian life, morals and fidelity to the Church’s Magisterium recommend them. It is fitting that such a one should have received a liturgical formation in accordance with his or her age, condition, state of life, and religious culture. [Sacrosanctum Concilium 19] No one should be selected whose designation could cause consternation for the faithful.[Immensae Caritatis]
The loophole here, of course, is that too often the clergy are the ones for whom there is a question or concern about life witness, morals, and fidelity. And we’ve seen the tragic consequences in many dioceses in which the bishop is the one in whom there is little confidence.
The other challenge is when “busybodies” go searching for a scandal to break.
What might have once been a logical and widely applied principle becomes a boondoggle both morally and ecclesiologically. When priests and bishops have lower standards of behavior, rather than equal or higher ones, then all administration along these lines has the appearance of favoritism, and even prudent decisions have a taint about them.