There are a great many things I have never understood about my fellow humans (e.g., taking pride in ignorance, praising belief without evidence in one domain while condemning it in most others, etc.). The one I want to address here is that of tradition: continuing to do things simply because one's family used to do them or because one's culture exerts pressure on us all to do them. I don't get it. And for the most part, I refuse to participate in it.
Yes, I am one of the small number of American atheists who does not celebrate Christmas. It holds no meaning for me and has come to represent Christianity and commercialism, making it just another pointless cultural tradition. I certainly don't condemn anyone else for celebrating it. If it means something to you, then have fun. All I've ever asked is that I receive the same courtesy. Of course, I recognize that will never happen.
Thanksgiving has never held any religious significance for me. When I was a Christian, my family regarded Thanksgiving as a mostly secular holiday designed to celebrate gluttony and football. I never really enjoyed it, including the traditional food. Even in my youth, I found it embarrassing to see my family give in to liberal guilt and invite people to dinner they never talked to the rest of the year. I didn't understand the "let's pretend we're much kinder than we really are for one day a year" routine. And then there were the years that we were told that we needed to pretend we were happy so as not to upset Grandma. Deny your feelings, kids! It is not like invalidating your child's emotions isn't associated with a host of mental disorders or anything. But the worst were the years we'd spend Thanksgiving with families who did think of it as a religious holiday. Even when I was a Christian, I hated those more than usual.
Now that I am an adult and have the freedom to turn my back on the entire thing, that is exactly what I do. I don't care for turkey, and I'm not about to cook one just because my culture says I am supposed to. For me, this is a much-needed day off work at a time when I nearly always need one. I can enjoy it on that basis, but I treat it like any other weekend.