I wonder if it is because we are fighting in the optimized version of the future that the Exos found for the Future War Cult.
I haven't been in the Vault of Glass yet so maybe it's answered there, but I assume like everything else in this game there will be more Questions than answers there.
-
It's a capitalized Noun. There's quite a lot of them in the setting. There's Guardians, wielding the Light of the Traveler against the forces of Darkness: the Fallen, the Hive, the Vex, and the Cabal. The Guardians train in the Crucible and work for the Vanguard. Also, they get sent on quests by the Speaker, the Stranger, and the Queen. Lots of Titles. Relatively few Names.