Why do atheists celebrate Christian holidays?
For the same reason christians celebrate pagan holidays…tradition. I know of no atheist that gives any religious significance to any holiday. it’s a day off with pay to most of them. Atheists don’t celebrate Jesus on December 25th anymore than Christians celebrate the solstice and all the other real origins of the holiday. If you show me there are masses of atheists lined up to partake in communion on Easter, then you may have a point. Otherwise, your question is simply not accurate.