Why would you use viewports?
To display views of paper space. You create, sclae and place viewports in model space.
To display views of model space. You create, scale and place viewports in paper space on a layout.
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.