Can you imagine being Leonardo Da Vinci in the 1400s trying to describe his ideas for machines that would allow humans to fly to the average person of his time? This is hundreds of years before the invention of electricity, the internal combustion engine, and many other things we take for granted today.
Holiday hiring is only useful if you get the right people, and the consensus among HR professionals is that the most consistent and efficient means of finding good people is to use word of mouth. Namely, this is because focusing on referrals means that only people who are already within your network will apply.