You've probably seen it at least once -- a house attached to a truck getting ferried to another place. It might look a little crazy, but people do have good reasons for moving a house. If you like where you live and have a good plot of land, you might want to build a new house on it. However, before you can build a new, larger house on your land, you'll have to get rid of the one that's already there. House demolition can be quite expensive, so you might be able to find someone who wants your house and will pay to have it moved. You'll likely not be selling the house itself for more than a dollar or so, but with the "buyer" paying the moving costs it can be a good deal for you.
You might also prefer someone to haul your house away rather than demolish it for environmental reasons. Having your entire house moved is really just a major recycling program. Better someone else now use your house elsewhere than have it broken into parts and chucked into a landfill.
On the flipside, if you love your house, but need to leave your land, you might also want to move your house then. You might need to leave your land for any number of reasons: it's too prone to flood or other natural disasters, you have a new job, you don't like your neighbors, suburban sprawl is encroaching on your land or perhaps the government has taken your land to build a new road. If you love your home, you don't have to leave it. You can buy a new plot of land and take your house with you. Moving a house can also be a great way to preserve a historic home.