I'm a long-time cruiser, but have never sailed over the "holidays!"
On the other hand, I've done cruises over Thanksgiving for many years. Sometimes the ship is decorated for that day, then for Christmas. Other times, there seems to be little attention paid to the December event!
I can imagine that some folks over Christmas may be down, either because their family has 'rejected' them or because they don't have family, anymore. That's sad; I hope their fellow passengers will embrace them and make their sailing memorable!
SWR