Is it not painfully obvious
Granted, Bitter Triumph is card parity, while this is card disadvantage, and haste is a big part of what puts Bitter Reunion over, but making Treasures is a way for Reanimator decks to hard-cast their big creatures and is just a generally powerful thing to do
While I can tell you that many more packs of Zendikar were manufactured than of Coldsnap, I cant tell you how big that gap is
Beyond that, the Pauper format specifically limits players to Common rarity cards, so it's the most budget-friendly way to explore with competitive play
A counterspell for noncreatures at two mana that also prevents your opponents from casting noncreature spells for the rest of the turn feels pretty powerful, even though its not without its limitations
This allowed Force of Will to be cast at anytime the player has a Blue card in their hand (and has more than one life)