The volume of shipments on the days before Christmas was so high Fed Ex and UPS could not make a significant percentage of the deliveries promised before the holiday deadline.
Sellers in e-commerce you certainly want every sale they can make. But to keep customers coming back, realistic expectations needs to be established. A holiday peak demand in the immediate days for the Christmas December 25th holiday can reasonably be expected. Organizations would be wise to not to say they delivery can be made by December 25, when there is a high chance that normal transit times can not be made. A earlier cut off date for Christmas delivery is good marketing. It always wise to create reasonable expectations for your customers.