Exactly which departed Christians would they have been communicating with? And given that they were still receiving devine guidance, perhaps redundant.
I take the point however, and in fact, do not seek the prayers of passed souls myself. But then I don't ask for prayers at all as a general rule. Bad on me.
Conjurring up the dead should not be attempted; however, speaking in the hope that they hear you is not the same thing. The differentiation is something that Catholics should probably spend more time discussing.
Whether or not I believe that souls of those who have departed this life are living or not has nothing to do with the ability or effacacy of communicating with them. Communicating with departed souls is strictly prohibited in scripture.
And when they say to you, “Inquire of the mediums and the necromancers who chirp and mutter,” should not a people inquire of their God? Should they inquire of the dead on behalf of the living? To the teaching and to the testimony! If they will not speak according to this word, it is because they have no light in them. (Isaiah 8:19-20)