Why do max and maude ride in the back of a big rig?

Max and Maude ride in the back of a big rig as part of their adventurous journey, seeking freedom and excitement away from their usual lives. The big rig offers them a unique perspective on the world as they travel across various landscapes, allowing them to explore new places and meet different people. Their time in the truck symbolizes a break from routine and an embrace of spontaneity.