Whether you want to protect your own win condition, or stop your opponent from resolving theirs, both of these cards can swing a game in your favor without you needing to hold up any mana
Pair it with Treasure engines like Kalain, Reclusive Painter or Prosper, Tome-Bound, and suddenly your plays become unstoppable, keeping opponents from interacting while you push damage
Why arent you
Not just because of the archetypal significance, but because casting this for double blue or double white in any other color combination sounds completely untenable
With both The Gitrog Monster and Underrealm Lich in play, survive until you draw a card, or put a land into your graveyard
Whether because of a rules nonbo or just lacking the legendary supertype, not every build-around is eligible to take command