Why will the Death Magnetic DLC show up in your Guitar Hero 3 setlist but not on World tour or Metallica?

The Death Magnetic DLC was specifically designed for Guitar Hero III: Legends of Rock, which allowed for additional downloadable content to be created for that game. In contrast, Guitar Hero World Tour and Guitar Hero: Metallica featured their own setlists and were structured differently, focusing on their respective themes and gameplay mechanics. As a result, the Death Magnetic tracks were not integrated into these later titles, maintaining their exclusivity to Guitar Hero III.