These days, with the snow consistently coming down, the roads keep getting worse and worse, along with the drivers. When the plows can't come and clear the snow, people tend to drive a significant amount slower so they don't slip, some may think this is overly cautious, but in reality, cars with summer tires still on their cars have a hard time driving in snow when they need snow tires. The winter tires provide more friction with the snow because of the lack there of with just the summer tires. Even with snow tires sometimes cars still tend to slip when accelerating too much on turns or speeding up in a hurry, again because of the lack of friction the snow adds to the surface. So even if you find the slow drivers annoying, they are the smart ones in this situation because they must be thinking of the lack of friction.