There is no intellectual rhyme or reason for leaving the physical world. It comes down to nature. Everyone in the physical world is connected. There is an invisible, intricate, almost spider web like connection that joins each living organism together on the physical plane and connects to the divine spiritual realm.
Even when a living being ceases to exist in living form on the physical plane, the connection is still very much alive in the spiritual realm. The memory and the love never disappear. It is always held tightly by those that were touched by the life now gone from the physical realm. You ask yourself why, when there seems to be so much life left in a being, so much to give to the physical world, why this being is chosen to be brought back to the spiritual realm? The answer is not easy to give. It is complex and complete understanding to those in the physical realm is not possible.
There are still connections to the one that has crossed over and there are still influences that the life of the person will continue to make even from the spiritual realm. Sometimes the influence is greater in the spiritual realm then in the physical realm. There are pacts made on a soul level and each individual organism that chooses to come to the physical plane, makes this soul pact in deciding when they will return to the spiritual realm. It is not an easy thing to describe.
The spiritual existence does not hold the same emotional and hormonal elements that the physical body holds, so you cannot look at it from an emotional perspective. Love exists. Love is an emotion, but it is also an energy, and the love that exists in the spiritual realm and that is present when a being makes a soul pact, is much different than the love that is felt emotionally in the physical realm. Love and light exist everywhere in the entire existence and through the connection between both the physical and spiritual realms. It is never ending. It is infinite. It is Divine. Amen.