Unlike any other creature on this planet, humans can learn and understand, without having experienced. They can think themselves into other peoples minds, imagine themselves into other peoples places.
Of course, this is a power, like my brand of fictional magic, that is morally neutral. One might use such an ability to manipulate, or control, just as much as to understand or sympathise.
And many prefer not to exercise their imaginations at all. They choose to remain comfortably within the bounds of their own experience, never troubling to wonder how it would feel to have been born other than they are. They can refuse to hear screams or to peer inside cages; they can close their minds and hearts to any suffering that does not touch them personally; they can refuse to know.
I might be tempted to envy people who can live that way, except that I do not think they have any fewer nightmares than I do. Choosing to live in narrow spaces can lead to a form of mental agoraphobia, and that brings its own terrors. I think the wilfully unimaginative see more monsters. They are often more afraid.