My guess? Because we've only been at this whole "civilization" thing for a few thousand years, and although that sounds like a hell of a long time when compared

My guess? Because we've only been at this whole "civilization" thing for a few thousand years, and although that sounds like a hell of a long time when compared with the few dozen years any one of us gets, it has so far not been enough for us to work out how we can reliably generalize at large scale the same altruistic instinct that so often and so regularly leads so many of us to risk harm to ourselves in defense of people we don't even know. It's probably not a very good guess. But what the hell, at least it's a guess that leaves room for the hope of a better future, and I like that a lot more than any of the alternatives that seem to be at hand.