Why do most people only show how thankful they are, sometimes, between Thanksgiving and Christmas?

Thanksgiving through Christmas, seem to make most people benevolent, giving, and thankful, OK maybe not the thankful. The news rewards those who donated a certain amount of turkeys, dinners, pieces of toys or wrapped gifts. The people who need, or could use those things, needed them all through the year, yet year after year, from what I can see, the majority do not pay attention until the holidays. Through out the year I always hear food banks and soup kitchens are saying their donations are down, but people needing help is up. People feel guiltier during the holiday, so they give more that they never gave through the year? Are people really more thankful because it is Thanksgiving? If they see how well off they are, compared to many on this planet, they should be thankful each day they fill their lungs with air.