Why does the Church not allow for the scattering of the remains of the dead?

At times, when assisting families in planning the funeral for a loved one, they become upset when I must deny their request to scatter the ashes of the deceased. This is especially true when they inform me that they are merely abiding by the wishes of their departed loved one. To deny this request is, in their opinion, a form of disrespect for the one who has died. But I see it in a different manner. To bury the dead respects both them and the living, who need a place to pray for the dead and a place where they can find comfort and consolation as they grieve. Offering the faithful departed a proper burial is indeed a great deed of charity for the deceased and for the living who continue to mourn their passing. 
 
The pious Catholic practice of offering the dead a proper burial was inherited from our Jewish ancestors in the faith. For the Jewish people, burying the dead was seen as a great sign of respect and charity on their behalf. In fact, when the Jewish people were in exile in Babylon, among the many trials they had to endure was that the Babylonians would not allow them to bury their departed loved ones, a way of mocking the conquered Jewish people and their beloved dead. Courageous souls like Tobit would go out in the dark of night and offer the dead a proper burial, a capital offense punishable by public execution (cf. Tobit 1:16-18). But it was worth the risk, because the Jewish people believed in the sacredness of the human body, created in the image of God, who created man as an act of divine love. Because of this belief in the inherent dignity of the human body, even after death, the body was treated with great honor and respect. 
 
For Christians, the understanding of the dignity of the human body went to a deeper level because of belief in the Incarnation of Jesus Christ . . . God becoming man. When the Word became flesh, God chose to take on a human form, which extols the sacredness of our humanity. This is why even the body of Jesus was treated with such reverence after He died on Mount Calvary. The body of Jesus was first placed lovingly in the arms of Mary at the foot of the Cross and then later lovingly placed in a tomb. Jesus was granted a dignified burial in the Holy Sepulcher, where His sacred body awaited the glory of the Resurrection. Therefore, our Lord has set forth the proper order for all of humanity: we must all die and return to the earth, where we await the glory of our resurrection. Catholics respectfully bury the dead because the body (immersed in the Paschal Mystery) is a sacred vessel, waiting to be reunited with the soul when Christ returns to consummate the age and establish the new heaven and the new earth.
 
Christians believe that a place of burial for the dead is also a sign of respect for the living, who need a concrete place to pray and mourn. When the ashes of the deceased are scattered, whether upon land or upon a body of water, the ashes become one with the natural elements. This becomes a vague and nebulous sense of their presence, which does not allow for a spiritual and emotional connection with the deceased. In contrast, there is something beautiful about going to a cemetery plot in which a loved one is buried. That place is sacred ground, a defined holy space, where their human body is interred, awaiting the resurrection. When Christians come to pray at a grave, they know they are in the presence of their loved one. This comforting presence helps in healing from the sorrow and agony of death. This is why in some cultures, Catholics gather for birthdays, holidays and anniversaries at the grave of a loved one and share in a meal there, even setting a place for their departed loved one. They remind us that the grave is indeed hallowed ground, where we pray for the dead and are consoled, knowing that we will be with them once again in the Kingdom.
 
There seems to be a contradiction to the command to bury the dead, namely when the relics of Catholic saints are found all throughout the world. But these relics are given a proper “burial” of sorts, in that they are placed in a reliquary and are given due reverence in Catholic churches and chapels. This is especially true of relics in the Altar of Sacrifice, where they are reverenced at every celebration of the Holy Mass. The revered tradition of venerating the relics of saints respects the need to honor their earthly remains, while also allowing Catholics to grow in holiness through their intercession. When we are in the presence of the relics of the saints, we can feel their presence and are moved to imitate their sanctity. 
 
As a pastor, my hope is that with the beautiful funeral liturgies of the Church and our prayerful support, we can offer comfort and peace to grieving families, by honoring and respecting their departed loved ones. But by insisting that the ashes of their loved ones be buried in a cemetery, we are also offering comfort to them for years to come. By praying at the graves of their loved ones, they are comforted and moved to conversion, as they reflect upon the reality of death. Praying for the dead, they also pray for their own hoped-for resurrection, so that they can forever be one with their loved ones in the glory of heaven.