Um, it was something the Pagans started celebrating and then the Christians stole it. We celebrate Christmas for the simple gift of giving. (But some believers will twist it and say well jesus gave the greatest gift ever. Ha! No.) It's about real giving. It's about giving to somebody else. You already have something and so you'd like to give to another. Thanksgiving was about being appreciative of what you already have; Christmas is about giving to someone else.
Cause It's a pagan holiday That originated with false gods. Jesus wasn't even born on December 25 so it has nothing to do with him. The shepherds wouldn't have been in the field on December 25th they would have been freezing let alone having a baby in a Manger.