John, it's a psychological group mentality. The more people are present in the group, the more each one thinks someone else will step up and do something, and the less responsibility is percieved as owned by each member of the group. In some instances, this is indeed false, when a group acts as one to help another in need without thought of individual selves. Howsoever, more often than not, each and every person in a group of onlookers each thinks that someone else will do what needs doing. Somebody will step forward. Somebody will confront. If not, then I will, but I'll just wait a moment just in case someone else wants to step forward first.
See how it goes? Sometimes herds move as one, and sometimes they don't. It all depends on the individual in the group. As an aside, questioning another's personal reasons and motives while giving none of your own, simply more questions and references to 'experts' is more than a bit unfair. How about answering your own question for once without relying on outside sources. As for me, I would step forward, and have in the past. Not out of hopes of glory, not out of hopes of press attention, but out of doing the right thing, irregardless of the cost. This is not based on some intellectual's viewpoint. It's simply part of the core of who I am. Like it or not, I am Me.