Yes, the Universe is vast and makes a very big playground, but the human race can be taken out by a rock or ourselves. Unlike some of our ancestors believed, I don't believe we're the center of the Universe nor God's only creation.
According to the spirit guides I have listened too we incarnate hundreds of times in a cycle of spiritual evolution, and we do so on many different planets though out the universe. We do this because as we evolve we need different experiences and go to planets that are more advanced.
It would be remiss of God to put all his eggs in one basket. Or all his children on one planet that can easily be destroyed. So the possibility that we can continue our evolution on other planets makes sense.
So is that the theory of the good die young, so the young kids that die of cancer have passed the tests and moved on to a better place, and were only here to teach us? So we do not remember our pass life's but its tucked away in our subconscious? Is this what your saying?
Life is full of suffering and some of it may be karma from past lives. I cannot say why children die, but they go to the spirit world and are brought up there. According to spirit guides we go to a higher realm when we die and spend as much time there as we need to assimilate our life experience. But until the soul completes its cycle of incarnations we have to reincarnate for more experience.
There is no pressure on us in the spirit world and we cannot evolve there. We need the struggle of the physical world to make us evolve.
According to my understanding the memory of all past lives is stored in the soul body. We have a number of higher bodies such as the astral and the mental body (see theosophy) We do not normally remember our past lives until our cycle of incarnations is complete. Then we have perfect recall of all of them