[ciokan]

That's probably because of the values and morals of our society mostly and not from a lack of empathy, heroism or selflessness. We inherit those values and pass them down to next generations. I think it's from the way we were raised and the way most of us raise our children. "If you do this, I will reward you with that"...this thing is from our childhood and sits at the root of mostly everything we do.

There are exceptions that make the rule I'm sure of it but our ego always tells us "it's not purity", "they can't be better than us", "they have a plan" so it's hard to distinguish. My 2c.