Because a child believing in Santa means parents are lying to their children.
Because when an enlightened child tells an unenlightened child the truth about Santa, the mother of the enlightened child gets an angry phone call from the mother of the unenlightened child.
Because the very premise of Santa is bribing children to behave well.
Because I heard a mother once say that her children had to "believe to receive", thus showing that her children had to perpetuate the lie in order to get gifts from the parents.
Because having Santa turns Christmas into a holiday all about receiving, not a whit about giving.
Because some people say they teach their children about Santa because "they don't want them to miss out on Christmas".
Because I have heard Santa described as "Whenever someone gives to someone else, whenever there is love, that is Santa." And that disgusts me.
Because twice now, when discussing Jesus, God, and angels, my students have brought up Santa.
And most importantly, because when one of my five-year-olds asked me if Santa was real, I couldn't tell him the truth, because 12 sets of childish, excited ears were listening, and I couldn't make myself break that many hearts (I didn't want 12-24 angry phone calls this afternoon either). Also, because today I told my kids that someday soon I will tell them about Santa, and I have no idea what I'm going to say.