Human Nature

I last left off, hoping to get a few examples that flow,
Why do we prefer to be in a crowd of well-off people in an expensive place rather than a group of weak diseased people, in tattered clothes in a slum area? It's human nature.
Why do like to spend more on "good" health care and not the food items, utensils, detergents etc used at home? It's human nature.
Why do we want to acquire money to live a lavish life later when we are un-able rather than living life now whe are, able? It's human nature.
I once read an article on the same topic by a good friend, who stated, that we as humans are very selfish inherently. We live for our each individual selves, you breathe to live, not for someone else, because you have a selfish desire to live. YOu may read this statement and understand several sides of it. But I am hoping you get the message I want to convey. We are selfish in every little deed that we do every second of our life and we have found comfort in labeling it "Human Nature".