I think it is supposed to delete it if there is nothing else using it on the page. It is supposed to go through all of the server behaviors and make sure it isn't in use before deleting it. It doesn't delete it always, because it may still be used by other Recordsets, Insert, Update, or Delete server behaviors. However, it is supposed to delete it once all of those have been updated on a page.
If it doesn't, and you are sure it isn't in use, then you can just manually delete it.