I am using MapView in v2 android google maps in a fragment but confused why we need to override all lifecycle methods?

Question

I am using this link https://stackoverflow.com/a/34626302/5761156 and taking reference from here https://gist.github.com/joshdholtz/4522551 but unable to understand why we need to override lifecycle methods such as on resume and on destroy . I tried not to override them and the maps then do not show? What am I doing wrong? Specifically I am adding the gist lines which I find confusing

@Override
public void onResume() {
    mapView.onResume();
    super.onResume();
}

@Override
public void onDestroy() {
    super.onDestroy();
    mapView.onDestroy();
}

@Override
public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
}