It actually used to kinda make sense. There were only a few "respawn restricted" areas in certain difficult activities. Places where the enemies were so powerful or numerous that their presence & defenses literally interfered with our Ghost's ability to revive us on the battlefield. And killing a champion would sort of "redirect" some of the energy on the field, giving our Ghost more strength to revive us with. But now that the portal forces us to run everything on increasingly higher difficulties, this lore no longer makes any sense. There are no more "normal" missions versus difficult missions. Every single activity in the portal forces you to face enemies that out-power you (or else get a bad grade & crappy loot). The entire frikkin portal has become one big "respawn restricted" zone.