For some decks, youll just be discarding irrelevant lands or spells too expensive to cast, but with some of the payoffs above, you can turn the discard of a loot effect into a game action as valuable as drawing an additional card
Imagine cycling through Flame of Anor, Lightning Bolt, or Olrin's Searing Light multiple times without paying mana
Youre not throwing the money hard enough
However, if an opponent's first draw is replaced (by Underrealm Lich's ability, for example), that draw didn't happen and Narset won't stop the next draw (which may also be replaced by Underrealm Lich's ability)
When you do cast Ulamog, you get to have an opponent exile the top half of their library, gone forever and out of the game
It wasnt uncommon to have eight or nine of these in your deck, and you often wanted more