For adults at least there's also the calculation of "What will this cost me?" You will see people with Downs syndrome force themselves between people fighting without considering that they might themselves be hurt, while the rest of us "normies" makes the calculation that there are twenty guys beating up a single person and they could just as easily take you out as well.

In professional settings we see people not speak out against obvious violations of proper conduct, ethical behavior and wrong doing out of fear. E.g. I know a nurse who should speak up about any number of violations in her workplace. They aren't serious enough to get someone killed and if she does she'll never work in this part of the country again. So yes, should should do something, but the personal cost is immense.

Actually, it does sound a bit sociopathic. Maybe it's just the average person succumbing to a sociopath society.