There are several reasons. One is that more people are on the road. Christmas shopping, for gifts and ornaments is part of the price of celebrating. People are also off to visit relatives, putting more traffic on the road. In this situation, people have to be mindful of their driving and pay attention to red lights and stop signs. It makes no sense to go through a red light just to save 30 seconds. Remember, you are not out in field circus, and there is no chronic "emergency" forcing you to get that extra door.
Perhaps the weather has something to do with it. Many parts of the country are seeing their first major snow of the season. Remember, even if you can drive fast in ice and snow, others cannot. You have to drive the speed of traffic, even if it's below the speed limit, for safety. Visibility is also a factor. It also gets dark earlier at this time of year than any other (the days are still getting shorter, but sunset is starting to come later about now). All this contributes to hazards.
Another is why I recommend starting your Christmas shopping as early as possible, even January. Too many people are scrambling to get that last-minute present, and this adds stress. People are paying more attention to what they are going to get their (fill in the blank) and where to get it than to the road. Getting the important shopping done before Halloween would relieve most of that stress. You can still go out in December, especially if you have children that you want to experience the fun of Christmas. You will, however, be in less of a rush. Getting Christmas decorations in October is also a good idea for the same reason.
Speed limits are posted for a reason. While I am not a strict stickler for following them, it is not a good idea to be doing 60 or 70 when the speed limit is only 30 or 35. Likewise, when conditions permit, if the speed limit is 45, you should not be doing 20 or 25 there (if you are accelerating out of a light, it's OK because that is the speed of traffic at that point). The general rule of thumb is to be doing the speed of traffic, but only if it's rational (if you are in dense fog and traffic is doing 60, that is too fast and the safe speed might only be 25). You should definitely pay attention to what's ahead of you so you don't hit that bicycle that is on the right side of the road where they are supposed to be (yes, some people still ride them all year long).
If you have a big load, you must make sure it is secure. Nothing is worse than having a Christmas tree flying off the car and into another windshield. Large presents should also be secure if you must carry them on top of the vehicle or in an open trunk. Too many people get into accidents when these things fall off and hit another car.
Most important, DO NOT DRINK AND DRIVE! This is probably the stupidest way to end up in an accident. You will not enjoy Christmas if you are in the hospital because you have been drinking and driving, not to mention the big fine, insurance premium spike, and even jail time for doing it. Here is part of a Christmas song adapted to this:
Dashing In the Snow
In a Beat-up Chevrolet
With the Beer We Go,
Crashing On the Way.
And the Police Cars Came
And the Ambulance Too
[missing]
(Chorus)
Drink And Drive
Drink And Drive
Drink And Drive And Die.
Oh I Wish
...[missing]
Drink And Drive
Drink And Drive
Drink And Drive And Die.
Oh I Wish...
No matter, you do not want to drink and drive and die. Or, drink and drive and end up paralyzed from the neck down, with your license revoked and having to pay a huge fine and getting your insurance more than double, plus have to lose sleep because you killed someone along the way. It is not worth it.