From what I recall reading, our 'Christmas tree' btw is a Germanic, pagan tradition for protecting the land spirits/ 'germanic fairies' from the bitter cold, in an attempt to appease them so they'd look upon the return of Light favourably - which was the original celebration of Yule - still the norwegian word for Christmas btw. They'd hang bells in the tree so they'd know that when it jingled, the fairy spirit was awake and present, and cookies on the branches as offerings.
Honestly, I find it kind of weird that christians consider 'christmas' part of their tradition, especially all the 'fun stuff' such as gift giving= germanic hospitality rules, santa claus = Wotan on the traditional 12 day Hunt, christmas trees, yule logs, the whole shebang. It's...about as pagan as it gets. Hell, many of them are practising sympathetic magic without even realising it
But, it is tradition to them. It aint so much about the religion, at least not when engaging in those activities. It's about coming together as a family, as a community at a time of year when -let's face it - we 're freezing our asses off and the lack of light is making everyone moody, lonely and blue. It's tradition and it brings the community together. And that's all that matters.
And yes, Easter aint Christian either, nor is Candlemas, for that matter or Halloween/Day of the Dead. People, including christians still celebrate it though, as a community.
So I guess...I could ask Christians the same question you re posing atheists