Grixis Affinity's entire plan depends on cheap artifacts reducing the cost of Myr Enforcer and Refurbished Familiar to zero, so Troublemaker Ouphe bargaining away a token to exile a key artifact land or Ichor Wellspring can strand their affinity threats at full price. Duress preemptively strips Reckoner's Bargain or Galvanic Blast before metalcraft comes online. Cast Down is a poor rate against a deck full of cheap, replaceable threats, and Fanatical Offering's card draw is less valuable than proactive disruption when they're racing to flood the board ahead of curve.