Beauty is in the eye of the beholder. By that logic, so is ugliness.
And every year on December 15th, people do their best to look ugly by wearing the ugliest sweaters they can find. To be honest, it's a tradition that pretty much lasts all of Thanksgiving until New Year's, because there's nothing people seem to love more than doing goofy stuff during the holidays and taking absolutely ridiculous photos. It's fun, it's sort of stupid, but most notably, it is easily the most important December tradition. And if you're going to celebrate this time-honored tradition of looking silly, you may as well go all out and look the silliest you're physically capable of.
Some of you may not find these sweaters ugly, but don't worry. Someone else does and that's what's important. Besides I'm sure there is an ugly sweater out there for you, too.