Nature in her infinite wisdom has only given us the capacity to embrace a certain type and amount of suffering.

Consequently we can only feel the suffering of those outside of our small circumscribed circle very lightly. 

Thus the loss of a little finger would cause us more pain than the death of five million people in some far off place.

We could take that as an indication of callousness, but actually, it is a limitation of capacity. We can only handle so much.