If you want to use standard runtime then yes, it is required. It acts mainly as wrapper around
OrthographicCamera so other render system can use it. You can access it from your system too if you add
CameraManager field to your class, it will be auto injected by Artemis.
In editor you can just set scene size to 1280x800, then there wouldn't be a need to manually init camera. There isn't any problem if you place elements outside camera bounds inside editor, you can later move camera using
CameraManager to make them visible.