heh..
Must be because after seeing how extra happy all the librarians are, the people realise their life must truly be down in the dumps if librarians can be that happy in their job!
j/k
On a serious note, it does kinda make sense though, xmas is a time of year where to most people, family is very important, and there are a lot of people who don't have a family to spend xmas with, or don't have contact with loved ones anymore etc, so I guess it's a time of year where people can get quite depressed.