Math Is Hard said:
I'm surprised they didn't help you. What a bunch of self-absorbed butt heads!
Your incident reminded me of an experiment we did in a social psychology class where we had to "accidentally" drop a bunch of pencils in a crowded area and observe who helped. Pretty much everyone in our class noticed that females are more likely to both give help and receive help. (Myself, I actually had pretty good luck with the guys when I dropped the pencils - I think maybe because I am older and they thought they were helping a teacher.) The guys almost never got help from other guys. In one case, one of the male students from our class wasn't even planning a "drop" and a group of guys happened to bump into him and scatter his pencils. They saw the whole thing happen, and knew it was their fault. But they kept on walking!
My favorite experiment was the Good Samaritan experiment, just because of the irony that was tossed in. Seminary students were required to go from one building to another to give a prepared talk. On the way there, they'd pass a person slumped in the doorway who would cough twice. The idea was to see how many of the seminary students would help the person laying in the doorway.
The variables:
Half of the group were to give a talk on jobs available in the seminary. Half of the group were to give a talk on the Good Samaritan parable.
One third of the group were given a prior task in the first building and released from it only when it was assured they'd be late in arriving to give their talk.
One third of the group were given a prior task to keep them from leaving early, but would definitely arrive on time for their talk unless they wasted too much time along the way.
One third of the group were released early enough that they had time to spare.
The amount of time the students had was the most significant factor in whether they helped the person in need. Ironically, at least a few seminary students that were late stepped directly over the person in need in their hurry to give their talk about the Good Samaritan

. Still, students on their way to talk about the Good Samaritan were more likely to help the person in need, even if the subject of their talk wasn't as significant as the amount of time they had to get to their talk.
http://people.eku.edu/falkenbergs/psy397/chapter8/sld015.htm
I think the tendency to ignore others in need is a matter of people being very self-centered and only thinking of others when it's convenient for themselves.
Personally, I probably would have helped a person I saw fall on the sidewalk, but only because the first thing I would probably do is laugh and I'd feel kind of guilty

. They probably wouldn't accept my help, but at least they'd have an opportunity to slug me.