I remember doing it--once. I got way too many people home, and wound up placing way too much littera-trash that my partner would make sure got in my call book. Good thing most of them were impossible to find again, since they could have made something like 5 or 6 attempted studies and made it mandatory for me to conclude each and every one of them to the point of baptism or a dead end.
They do this to see how much stupid tribulation they can make the witlesses endure. You go out, waste your day off on stupid things (and there is a boasting session that evening, to boot), and pxxx off everyone. Usually, nothing gets accomplished. You might get littera-trash in the hands of more people (and in the rubbish or recycling bin the next day). But, have fun trying to get most of those people again--usually they will be at work or busy the next day.
And Christmas is even worse. Imagine a 7-year old child eager to get into that pile of Christmas presents under a well-lit Christmas tree, when the parents get the witlesses to hold them up. This child knows he is going to have to wait until the presentation is done and the parents are back to the tree before any of those presents can be open. And, when you are 7 years old and about to open your Christmas presents, 15 minutes seems to go on forever. Each time you seem to be winding down, a new point comes out--and, before long, half an hour (or a whole hour) has gone by. All this to place a fxxxing set of rags, that are probably going to end up in the rubbish half-read once the witlesses are gone.
Then, this sets a miserable tone for the remainder of the day. The delay robs this 7-year old of much of the joy, and by the time the witlesses are gone, there is usually much fuss. What started out as a peaceful morning with the anticipation of getting those presents open often ends up with screaming, sobbing, and time spent in the room (or a spanking). It adds to the stress--Christmas is already a stress, albeit a positive one. The added stress, however, is negative and can ruin the experience for children that just want their damn presents.
For this reason, I hope the witlesses have a dreary Christmas (that is, one where no one responds or point blank tells them that they are not interested in their scam) and a crappy new year (one where no one gets baptized, disfellowshippings happen every day, and no one is ever interested).