Doing what's right

I wonder why people don't do what's right. It seems like such an easy thing to do--no problems, no stress. But what possesses people to act in such a way for the express purpose of making life difficult for others? Why are some motivated to spend the time--and sometimes an enormous amount of time--to create problems for no other reason than to cause trouble? Imagine what the world would be like if everyone lived their lives with this premise: Do no harm. So elegant, so simple, yet so elusive.