The most important reason that I have a winter tire and wheel package is that it gives me the ability to put my snow tires on myself.
Last winter, I was away on a trip the weekend of the first snow. I flew back in town late Sunday night, caught a ride home, and went right to bed. I woke up to find 2 or 3 inches of snow on the ground, and my car was still sitting on my its big, wide, slick Dunlop Direzza Sport Z1 Star Specs.
As much as I love the Dunlops, they would not have made it out of my neighborhood to get me and my snow tires to an installer, but having the snows already mounted on wheels, I was able to get up, put the tires on, and still make it to work on time.