Why would you use viewports?
To display views of model space. You create, scale and place viewports in paper space on a layout.
To display views of paper space. You create, sclae and place viewports in model space.
To save specific views of a 3D model. Then even if you rotate or move that model, you can jump back to the saved view.
To save specific views of a 2D model. Then even if you rotate or move that model, you can umped back to the saved view.