Imagine having a chicken dinner on Thanksgiving!
What would Thanksgiving be without the turkey and the trimmings? To many people, it wouldn't be Thanksgiving. Ironically, we eat more chicken than turkey on a year-round basis. However, we have grown accustomed to eating turkey on Thanksgiving Day. Having a chicken dinner would be a big change that few people would accept.
It has to do with our perception. Humans are creatures of habit. We like stability and dislike change.
