Most people will help those in need, period. Regardless of whether or not they have the training/skills/knowledge whatever, they will try. However, if you take a first aid or wilderness first aid class, they teach that when you find a someone injured one of the first things you need to do is determine if the "scene is safe". If there is a risk to you, you have to determine whether or not to proceed.
The same is true in many other aspects of first aid and rescue. One victim is better than two. Now, this really depends on the situation, but I will probably not put my own life in jeopardy for someone else's, especially someone I don't know or have never met. Maybe that's selfish or unreasonable, but I like being alive. If there is no threat to my life, heck yeah I'm gonna help you.
Search and rescue personell do the same thing. Look at Mt. Washington. Many many rescues have been delayed to wait out better weather. People have died up there because the rescuers didn't feel it was safe to go up. Think about the Madison rescue thread- if the weather had been god-awful and the SAR team couldn't go out that night and those kids died- would we be calling the rescuers "murderers"?
As far as I can tell, at high altitude, just being up there, let alone rescueing someone, is a serious risk to your life.