I don't know how to be more clear about this.
They are ON THE RUN, trying to avoid capture. To do this, they have to constantly be on the move. They camp in the woods on night, then they drive across state. Maybe they have enough cash to stay at a hotel - they can't use a credit card because doing so will show their location. They drive further away. They can't stay in one place, because they must try constantly to avoid detection.