The cursor is needed for you to interact with al the menus, apps and other game features, which are availalbe at any time during gameplay. In BeamNG.drive the mouse primary role is for the cursor itself, not the camera like in ETS2.

This is why Euro Truck Simulator 2 made this setup a default after experimenting with it for dozens of hours, and which is now a habit for hundreds of thousands of people. In order to view the surroundings and use the mouse you have to use the WASD. To move the camera with the mouse you necessarily have to hold the RMB (you can also move the camera with the numpad keys, or the right thumbstick on an xbox controller) The thing with the camera is not possible currently. You prefer WASD over Arrow Keys, and the game allows you to change all the controls to what you prefer.

Because everybody's has different preference.