I think because you dont update them, so nobody knows, that they exist.
Adding a scenario icon to your MEDUSA game might help; and brick-breaker is a common game on the site. These may be some influencial reasons why they do not get very many hits (although 150 in a month for the brick-breaker scenario is not that bad).
Interacting with others is might also help. So go out and look for some nice scenarios and like them! Maybe those people will like yours too.