Jehovah's Witnesses do not celebrate holidays because of the pagan origins of the holidays. Christmas traditions are basically the same as the pagan traditions of Yule and Saturnalia with Christ thrown in to make it palatable to Christians. Halloween is the pagan holiday of Samhain, repurposed as "All Saints Day" to make it palatable to Christians. Easter is the pagan celebration of the spring Equinox with the death and resurrection of Christ thrown in to make it palatable to Christians.

They are right, all these holidays are simply pagan traditions with Christ thrown into the mix in order to allow Christians to feel comfortable partaking in pagan rituals. Nevertheless, I disagree with their refusal to celebrate these holidays. I believe pagan ritual and tradition are harmless when stripped of their meaning and have been turned into a good thing by being coopted by Christianity. The origins of the rituals are irrelevant, it's the meaning behind them that matters and that meaning is no longer pagan but has become Christian.