The usual idea of a “backup” is that it can be used to restore from if the “original” is lost or damaged. Everett worlds are not “backups” in that sense of the word. If a quantum grenade kills someone, their grieving wife and daughters are not consoled much by the fact that—in other Everett worlds—the bomb did not go off. The supposed “backups” are inaccessible to them.
The usual idea of a “backup” is that it can be used to restore from if the “original” is lost or damaged. Everett worlds are not “backups” in that sense of the word. If a quantum grenade kills someone, their grieving wife and daughters are not consoled much by the fact that—in other Everett worlds—the bomb did not go off. The supposed “backups” are inaccessible to them.