Even after EnableViewState="false" page source show view state

'EnableViewState' property is used to indicate whether the server control persists its view state, and the view state of any child controls it contains. it has nothing to do with the text exist in '__VIEWSTATE' in page source.
It is true that 'EnableViewState' set to 'false' will decrease the content size of '__VIEWSTATE' text.
if you want to completely remove the text from '__VIEWSTATE' you can add below events in page load

 protected override void SavePageStateToPersistenceMedium(object state)
{
    //base.SavePageStateToPersistenceMedium(state);
}

protected override object LoadPageStateFromPersistenceMedium()
{
    return null; //return base.LoadPageStateFromPersistenceMedium();
}

protected override object SaveViewState()
{
    return null;// base.SaveViewState();
}