Except for asking for the intercession of canonized saints, our main contact with those who have gone before us should be praying for the souls in Purgatory.  In other words, we’re supposed to be praying to God for them, not usually discussing things with them. It is true that we can ask souls in Purgatory for help, but that has to be done in general asking their intercession, not specifically. In fact, it’s either St. Alphonsus or St. Bellarmine who teaches that such requests on earth for intercession from the Holy Souls in Purgatory must be addressed to God first to then He asks the Holy Souls to intercede. (It’s kind of reverse order from our normal requesting up the chain of command as Catholics.)  In any case, the doctor of the Church probably proposed this notion of going to God to ask Him to have Holy Souls intervene for us on earth so as to keep the faithful on earth far away from being tempted to communicate with specific deceased persons. This could come dangerously close to seances, as seen below in 1 Sam 28 when King Saul is punished (first his disobedience in battle) but then for a seance with the Witch of Endor in trying to contact the prophet Samuel.  This is the final straw in losing the Kingdom of Israel:

Saul disguised himself and put on other garments and went, he and two men with him. And they came to the woman by night. And he said, “Divine for me by a spirit and bring up for me whomever I shall name to you.” The woman said to him, “Surely you know what Saul has done, how he has cut off the mediums and the necromancers from the land. Why then are you laying a trap for my life to bring about my death?” But Saul swore to her by the Lord, “As the Lord lives, no punishment shall come upon you for this thing.” Then the woman said, “Whom shall I bring up for you?” He said, “Bring up Samuel for me.” When the woman saw Samuel, she cried out with a loud voice. And the woman said to Saul, “Why have you deceived me? You are Saul.” … Then Samuel said to Saul, “Why have you disturbed me by bringing me up?” Saul answered, “I am in great distress, for the Philistines are warring against me, and God has turned away from me and answers me no more, either by prophets or by dreams. Therefore I have summoned you to tell me what I shall do.” And Samuel said, “Why then do you ask me, since the Lord has turned from you and become your enemy? The Lord has done to you as he spoke by me, for the Lord has torn the kingdom out of your hand and given it to your neighbor, David.”—1 Sam 28:8-12, 15-17.

There is no sin in brief communications to those asleep in the Lord, like, “I miss you Dad” or “I forgive you, Mom” or “I hope you made it to heaven, grandpa.” But long, ritualistic communications with the dead is the sin of seance or necromancy.  Notice again that Saul committed a great sin not in trying to contact a bad person but trying to contact a good person—the prophet Samuel.  (Of course, the sin would be greater if one were to try to contact a wicked deceased person.)  But Saul still lost the kingdom in trying to contact a good person.  (Of course, this was clearly before the days of the Catholic Church’s official canonizations.  We can now pray to the prophet Samuel, as he went from the limbo of the Fathers to the beatific vision on the very first Holy Saturday. In fact, the prophet Samuel is canonized in the old Roman calendar and Roman Martyrology on 20 August every year. But asking for intercession of the saints is clearly different from seances or necromancy.)

Again, we can ask the intercession of saints officially canonized by the Catholic Church, and even have conversations with them. Not so with our deceased family and friends, except the aforementioned exceptions to this rule. One additional reason for this is that we have to remember that many people we suppose are in heaven are—in reality—still suffering in Purgatory (or already in hell for eternity.) But we’ll avoid the scary topic of hell today and just stick with the Purgatory topic at-hand: Many people project their warm feelings for a deceased family member upon their own theology, erroneously believing this is God telling them interiorly that their loved one is already in heaven. But few things could be more uncharitable to our faithful departed than “canonizing” them prematurely if they’re still in Purgatory. Why is this so uncharitable? Because we deprive the souls in Purgatory of our much needed prayers when we erroneously place them in heaven before they get there.

In fact, in my own living will and testament, I beg my friends to pray for my departed soul constantly until their own death in the case that I’m saved (please, God!) and yet I still have much time to do in Purgatory.  Unless I die a martyr, I truly beg you to pray for me—not to me—if you should hear of my death before yours.  Please, this would include as many requiem Masses as possible for my soul, as well as numerous Eucharistic all-night vigils.