We feel it, around Christmas. It's a kind of generosity that doesn't really exist during the rest of the year. Kids get excited about buying things that they are going to give away. Charitable organizations see a stream of extra income as people look outside of their own lives to touch the lives of others. Trees with wish-lists on them become bare as people give and give and give.
Why? Is it a grand exchange, everyone just giving to receive? Is it just cultural - people would feel like they didn't fit if they didn't do it? Or is there something about the message of a Father giving his Son that moves us to realize that generosity is just...better?