Some holidays are religious based. Halloween or All Hollows Eve is a night to protect homes from the devil and evil spirits during the Middle Ages. It is linked to Christianity, so is Easter and Christmas. The US was formed by Christians and Protestants, so yeah ever wonder why the pledge of allegiance has God in it? There you go. There aren't as many holidays that don't have religion linked to them. Thanks giving, independence days, and stupid holidays like arbor day aren't.