I'm sorry but I don't understand the reason. I've read a bit about the "Spiritualist" movement. It grew out of phony mediums like the Fox sisters. If there is afterlife energy we will find out soon enough. I think that most of us have unresolved issues or things we wish we could say to our departed loved ones but I'm not sure that there is any resolution in that through spiritualist churches or mediums.
If you choose to pursue this I wish you the best