When I was growing up, we needed a vehicle that could tow and haul the family and my that my parents used for going over the Sierras in the snow. An SUV made sense, it was taken off road enough that it got used. We also had a truck since we used firewood for heating and regularly were hauling things around. Now, they don't go up to work in the snow like they used to, so they no longer have an SUV, and now they have an extended cab truck, but it still gets used for truck duties. When you have five acres of land, you find uses for a truck really fast.
Heck, I find enough uses for my own truck (albeit, a much smaller one) that if I were to replace it with a car I'd definitely get a small box (xB, Caliber, HHR type thing) or wagon such as the Magnum.
So while it's true that most people don't need them, there's a good number of people that do.