I think there is a function that defines our socialized compassion. I always expected that in a city like New York
it would be easier to just ignore bad things happening - truthfully, I'm sure it does, and due to our density, it happens more often than in the middle of nowhere. But there is something about the constant overlap with people who seem to be unlike you but you realize, in the moment, they're exactly like you. It would be distressing, except it happens constantly, and so it just is. Little things just add up and make an impression.
Once, on a the subway late at night (as if you could tell, wandering about underground) a group of young black men got on our train, being rowdy although generally not scary. There was a homeless guy sitting next to us, sound asleep. They started pitching pennies into his open coat pocket. It seemed harmless enough, and I was unsure how to respond. We went a few stops, and the group starts getting organized to leave at the next stop. Then, the one who initiated the penny pitching says "Hey, hey, let's do this right." or something to that effect, pulls a dollar out of his pocket, and holds his hand out. They all dig around, and come up with about 10 bucks and carefully placed it in the sleeping man's pocket. It was so everyday and so compassionate all at once (notice I have no idea about what the function that defines our compassion is...).