One person selfishly drops a piece of litter on the ground, the other selfishly picks it up.
Everything we do is done because it's better than not doing it. "Better" is the complicated term. Better might mean, "gives me physical pleasure right now," for some people, while better might mean, "the story I tell myself about the contribution I just made gives me joy and satisfaction."
Society benefits when people selfishly choose the long view and the generous view. The heroes we look up to are those that sacrificed to build schools, to overcome evil, to connect and lead–even though it didn't necessarily help them in the short run.
Culture, then, provides the bridge between childish, naive instincts to only do what feels good now, to only help ourselves and maybe our kids. Culture makes it too socially expensive to brag about not giving money to charity or, to pick an absurd example, to kill the infirm and the less fortunate. We reduce sociopathic behavior by establishing norms and rewarding those that contribute while shunning and punishing those that don't.
Marketers have a huge role in this, because we are the amplified culture creators. When we sell people on quick satisfaction now, is it any wonder that people buy it?
In the US, today some people will give thanks for what they personally have. Others will focus more on what has gone right for family and friends. And others will dig deeper and think hard about what they can do to take an even longer view, and to create a platform where even more people will be thankful a year or a decade from now.
Sure, we're all selfish, but our culture rewards those who take their selfishness to the long-term, to the narrative of leader and caretaker and gardener, not merely self-interested consumer.
One of the greatest things to be thankful for is the fact that we live in a culture that pushes each of us to be thankful and generous. It didn't have to turn out that way, and I'm glad it did.