By winter's onset, daylight was short, the harvest was finished, and all winter provisions should have been stocked. During the Twelve Days all work was forbidden, other than necessary care of farm animals and daily meal preparations. The applied equally to "women's work" such as spinning, even though it could be done indoors where it was warmer. This prohibition on work during Yuletide was even set into law by the Anglo-Saxon king, Alfred the Great.
There were other incentives to be sure that all chores were completed on time - any work attempted during the Twelve Days would be undone or spoiled: the "devil" would cut down any flax left on the distaff (a staff to hold unspun fibers); milling would cause all grain within earshot to go rotten; laundry hung out to dry would be carried off by Odin's pack of wild dogs; etc. The reward for meeting the deadline was twelve days off - a generous holiday break even today. January 7 was called "St. Distaff's Day" - a tongue-in-cheek name for the end of women's leisure (there was/is no saint by this name). Men, on the other hand, were off until "Plough Monday" - the first Monday after the Twelfth Day.
I know that while cleaning the house for Christmas Eve dinner I felt like I was earning my twelve days of rest, and am glad it has come! Merry Christmas to you and yours from all of us at Twelve Days!