Christmas, unfortunately, stopped being a religious event long, long before the first Unioc smuggler celebrated it. Those few religious purists remaining among the humans might claim that galactic culture corrupted the holiday, but most 31st century historians are confident that the fault can be squarely placed on the television producers responsible for 'Rudolph the Red-Nosed Reindeer.'
In most Galactic Languages, the expression "Merry Christmas" differs in meaning from the phrase "Look at what I bought for you" in only one way. Idiomatically, it means "Look at what I bought for you" with the unspoken-but-fully-expressed sentiment "No, you may not have the receipt."