maintaining an inactive Drupal site can be a pain. There is a constant stream of security releases that you need to apply. And it's really maddening if you apply a security release to an inactive site only to find out the release contains other changes that break things that used to work, so that you have to spend time trying to get that inactive site working again. Not to mention that it's expensive to pay for hosting that can securely deploy Drupal sites if you aren't even using any Drupal interactivity any more.