It is every christmas though
Because when you are the parent and you want a few christmases off in a row because your child is small and still enjoying the magic of christmas you think sure, your childless colleague can suck up a few working christmases, its only a few years.
But then Sarah gets pregnant, then tina, then Gemma and then all of a sudden that childless person has covered all the christmases and funnily enough the parents aren't rushing to make sure that childless person ever gets a christmas off.
I've even been told that I should work Christmas because someone wanted to spend Christmas with her adult children. But she couldnt understand that I might want christmas off to spend with my parents.
It is every Christmas because there is always another parent.
Theres also an absolutely assumption that every parent is a delight and you are wrecking a childs christmas if they arent at home. Funnily enough Ive worked with people we knew were horrific parents, report them to social services levels, and yet still at christmas I was expected to work so that their child could experience the magic of being hit by their mum on Christmas day. Happy fucking christmas!