Sometimes when annotating a plan manually or putting a new door into the model in another view, some elements slip your attention. Once you stumble upon an unannotated object, you pick the 'create similar' option from a neighbouring similar object's annotation's context menu and tag the new object. Only you did not pay attention to the tick on 'leader'. No matter whether the annotation you are trying to use had a leader or not, Revit always uses the last option actively selected by the user when last using the annotate command.