Thought this was a cool one from Dave Canterbury. Cold weather trips and long stints in the wilderness will often require more gear than you can reasonably carry on your back - especially if you've got some real distance to cover. A sled like Dave's (more properly called a pulk) allows you to carry substantially more weight and gear for less effort.
Being a survivalist type dad with two young boys, I see it and think about kid transport, too.
For the less snow covered parts of the world, a cart could be rigged in a similar fashion and pushed or pulled to move around. Not a tactical shopping cart or wheel barrow full of guns. One of those heavy duty garden/utility trailers capable of supporting mass quantities of weight would be the starting point. Or you could grab some mountain bike tires and fab up a simple frame without too much trouble. I've got that project filed away for a rainy day.
A reasonable sized family dog could be trained to do the pulling, too. Probably actually enjoy doing all the hard work, too! Sucker.
Anyways, if you had to be on foot and were looking at a long distance and a long while, a sled or car loaded up with a couple extra hundred pounds of supplies would be a huge advantage and up your survival odds.