It's not "forbidding" something, really. "Shall not" could just as equally be translated to "it is inadvisable to", in most of these cases. The reason that is followed by reasoning of why such a thing is pointless, is because it is saying that something should not be common practice. It's setting a policy, not a regulation or law. A guideline for clergy to follow:
The reason for the act of communion and the dead? It was common at the time for someone purporting to be a Medium or related spiritualist or magician of some kind, to say that they could act as an intercessor. Sometimes with quite the hefty fee. They'd claim to distressed families that the Eucharist was required to save the family's deceased, and that through themselves the lost one could be saved.
In short, conmen are conmen. The church had plenty of con artists that they tried to work around. The church was telling their leaders not to engage with them, by making this particular policy. If the fees for Medium services had been less, then the policy probably still would have eventually been created, but it wouldn't have been part of such an important meeting.
It plays into the greater context of that particular Council - there were many people making claims to be bishops, or deacons, who were bringing with them a religion that was more syncretic in nature (combining existing religious beliefs), and the church was attempting to stamp that out and establish a structure to prevent it continuing. (Which they ultimately failed to do, as seen by the African diaspora religions).
The reason for the act of communion and the dead? It was common at the time for someone purporting to be a Medium or related spiritualist or magician of some kind, to say that they could act as an intercessor. Sometimes with quite the hefty fee. They'd claim to distressed families that the Eucharist was required to save the family's deceased, and that through themselves the lost one could be saved.
In short, conmen are conmen. The church had plenty of con artists that they tried to work around. The church was telling their leaders not to engage with them, by making this particular policy. If the fees for Medium services had been less, then the policy probably still would have eventually been created, but it wouldn't have been part of such an important meeting.
It plays into the greater context of that particular Council - there were many people making claims to be bishops, or deacons, who were bringing with them a religion that was more syncretic in nature (combining existing religious beliefs), and the church was attempting to stamp that out and establish a structure to prevent it continuing. (Which they ultimately failed to do, as seen by the African diaspora religions).