And that is a good question. I did NOT participate for that reason for the first two years. And found my feelings of marginalization during December to be doubled because this is exactly the sort of challenge I love. And it only exists like this. Not only wasn't I going to the big party everyone else was so excited about, I couldn't even go to the more fun one which actually had food I could eat.
Finally, after two years, I, with tremendous guilt, decided to participate. It wasn't the most positive of experiences the first time, but that was just luck of the draw, and I decided to do it again the following year.
And found myself so distracted by the story that the normal raving bitch of December didn't show up until fairly late in the game.
But I may have whined myself out of participating this year.