Rebirther was created as a tool for druids and any other raider to monitor Innervate and Rebirth availability regardless of whether the druids in the group have the addon. Instead of having to look up who’s in your group, who’s dead and then going through a list of cooldowns attempting to deduce what druid might have his Rebirth or Innervate available, you can just look at the clean list presented by Rebirther to easily see the state of all the druids’ cooldowns.