Because everyone knows if you don't wave to Macy's Santa at the end of the parade, you won't get any presents!
I used to actually believe this! Just another instance of my mother brainwashing my sister and me as small children. But now I instinctively find myself watching all the Macy's Day parade and waving and making everyone watching it with me do the same.
SO make sure you WAVE at Santa!!!
Have a very happy Thanksgiving everyone!