I would imagine that most people experience this. Why are some people greeted with infinite love and dead relatives and some greeted with existential nothingness?
I would not say those people were greeted with "existential nothingness". I'd suggest their consciousness simply didn't "detach" from their body. What they experienced is much the same as what we all experience in the deep dreamless sleep.
Also, near-death experiences can and do frequently occur in circumstances where the body is not shut down at all - such as a car accident that is narrowly avoided, a fall off the mountain where the person is saved by their climbing rope (and hence does not sustain any serious injury at all), and, rarely, spontaneously in people who are neither near death nor in significant peril. This is why many simplistic materialist "explanations" fail to hold water - they talk about things like oxygen deprivation, brain trauma, and the like, and phenomenologically similar NDEs occur in all kinds of different body and brain conditions - awake, asleep, in a coma, flatlined, and completely unharmed.
My view is that everyone will have something similar to a near-death experience when their body dies permanently (although it is likely for some it might be preceded by an interlude quiet unconsciousness). I view the brain as a filter that blocks much of the light of consciousness / reality, and when the brain's life ends, we will be much more open to the whole of reality. I fully expect that our individuality will be reduced after death - perhaps I will view "Matthew" as simply a dream I had for a brief moment, and I will savor his life, the good and the bad of it, seeing it in the context with everyone else's life in a more objective way. By the same token, I do not expect a complete loss of individuality either.
As to the existential question why some get to have this kind of experience (which is generally life-transformative) and why others do not, that is itself a deep mystery. I have not had a near-death experience, but I had a very powerful spiritually transformative experience at age 18, and less intense but also very meaningful experiences other times in my own life. And I talk to many people who have never had anything similar.
In some ways it seems profoundly unfair: why should some be given a "vision of heaven" and others not? It is much easier (in many cases, trivially easy) for people with profound spiritual experiences to accept life after death, the meaningfulness of existence, the importance of love, the connection between all of us.
It certainly doesn't seem to be the result of a special moral character that experiencers have. More like an incredible, beautiful gift, unearned and undeserved, an opportunity to see the depths of reality that most are not given.
In my 44 years on this planet, I have come to realize, more and more, that God loves diversity. Diversity in all its forms. If, as I believe, it is ultimately God that is perceiving all reality and experiencing all lives, then it seems God wishes to view Reality from every possible vantage point, saint and sinner, atheist and believer, male and female, oak, fox, eagle and human being. I think God wants to see what each one of decides to do with our lives, given our abilities, experiences and beliefs. And from all of this, the most beautiful yet poignant and inexpressible story is written in Mind (which is ultimately all that exists).
I don't know everything. Far from. But this is what my own life tells and shows me is going on. And each day I have left, to love others, to share, to reach out, to connect, to smile together. This is what I am trying to make my life about.
. Sin is thus made hugely significant, so there will be an unbelievable huge debt to be forgiven of and thus result in an unbelievable huge “Love” (Godly type Love). 
