Bant Control is loaded with blue spells (Force of Will, Brainstorm, Ponder, Tamiyo, Quantum Riddler, Force of Negation), making Red Elemental Blast a premium answer that both counters and destroys key permanents or spells. Void Mirror punishes their free Force of Will and Force of Negation, cast by exiling a blue card rather than paying mana. Trinisphere and extra Chalice of the Void copies are weaker since their curve includes efficient one- and two-mana plays (Swords to Plowshares, Leyline Binding at reduced cost, Ponder) that a blanket tax doesn't meaningfully punish, and we'd rather hold interactive answers than clog our own low curve.