Christmas is much more understated in Spain than in other parts of the western world. It's a religious holiday, spent mostly at home with family. The big whoopie of gift-giving and bell-ringing is saved for New Year's Eve and Three Kings' Day (Jan. 6/epiphany.) Hereabouts there really IS a "12 days of Christmas," which means pilgrims face special challenges some days finding places to eat, sleep, or shop.
Christmas Eve is the first -- most places close all day, some are open for only the morning. Churches are full.
A whole lot of albergues close, as the workers want to be at home like everyone else.
Christmas Day brings closed grocery stores, restaurants, pharmacies, and often albergues.
Things ease up a bit until New Year's Eve, New Year's Day, which is kind of a repeat of Christmas, pilgrim-wise. Stock up in the morning with some food for the evening and the following day.
The whole business winds up on Epiphany, when the Three Kings bring toys to good girls and boys, with parades in the streets and everyone going home to celebrate with granny. Once again, pilgrims find themselves phoning ahead to find an open albergue or hostel. The Aprinca or "Winter Pilgrim" lists are invaluable for this.
Plenty of pilgrims still go for it. You don't ever hear of fatalities, so it must be do-able!
All that said, I do know the two friendly hospitaleras at Albergue Municipal de Najera are planning a nice Christmas dinner for whatever lucky pilgrims find their way there!