Joomla does not oblige extensions to follow a specific convention for naming folders and database tables. Past experience has shown that making such assumptions is wrong and doesn't yield the desirable results. As a result we cannot offer a feature which our experience tells us it will be broken by definition.
Finally note that developers leave database information behind because of the very loud and very small minority of shouting morons. Said morons uninstall an extension before updating it –for reasons unknown, despite documentation and common sense– and then get all pissy about the extension's data having been deleted. Since these morons shout louder than reasonable people like you and me who expect uninstallation to be complete they get their way and we get to clean up crap on our sites.
Nicholas K. Dionysopoulos
Lead Developer and Director
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