Demons and their human collaborators (see http://vimeo.com/34635784) have, for six years, have attempted to prevent masturbation by their victims.
It is not known why; but, the demons, those pictured in the video, and others have spent an inordinate amount of time and energy outside windows and doors insuring that any type of sexual activity by their victims is thwarted or disturbed or otherwise made uncomfortable enough to generating anxiety and phobia regarding sex. The end result may also be to cause enough anger in the victim to cause the victim to lash out in ways they otherwise would not.