I see you quoted a lot of people from the UK, and it's worth noting that the UK loves Christmas, generally speaking. But the UK is not a nation of practicing Christians, to say the least.

That brings to mind the years I lived in Montreal, the largest city (by far) in the Canadian province of Quebec, and the center of perhaps the most atheist society on Earth. (Christian Quebecois exist, but finding one is kind of like finding a truffle. You know they're there, but they're so rare!)

Anyway, Montreal is famous for Christmas traditions and warm family festivities. Special Christmas foods include traditional meat pies that might seem odd to Americans, but the sweets inventory is much more familiar.

I celebrated many a Christmas in Montreal with Montreal families and not once did anyone pause to ask, "Why are we doing this since we haven't been Christians for three generations?"

It just never came up.