So, JW's don't celebrate Christmas or other holidays. Why? As Bill Cetnar once said, there are two reasons for everything: the reason they tell you, and the REAL REASON. They will tell you it's because Christmas is "pagan" and can lead to all sorts of licentious conduct (like drinking too much MacAllan Scotch?).
Now for the real reason: JW's are not allowed to celebrate because it's an easy way to get their families angry at their self-righteousness and superior attitude, which feeds the JW's persecution complex. It alienates the JW from family members and former friends, giving the borg more control over them. It feeds the JW sense of moral superiority and inhibits fun and merriment. It saves them money, which they can then donate to their narcissistic masters in New York.
What a clever ploy!