I am generous with what I have—I choose to be generous with what I have—precisely because we are no longer committed to one another as members of a shared social structure. Instead, the shift of responsibility for the public welfare toward private entities displaces our obligations to one another in favor of individual liberties and, I think, leaves us queasy about the notion of obligation altogether.
The game theory of things tends to pull the society apart, particularly when it is easier to see who is paying what. If the richer end feels they're paying more than their fair share, this can tend to break things down.
I suspect that Francis Fukuyama has a bit to say about this in how democratic societies built themselves up over time. Similarly one of his adherents Jonah Goldberg provides some related arguments about tribalism tending to tear democracies down when we revert back to a more primitive viewpoint instead of being able to trust the larger governmental structures of a democracy.