Probably because this is cheaper to combo with the new spell damage minions. Against aggro, you place down a body and clear their board, and doing that one turn early means more tempo + clear, which is a big deal. My guess is that if mages do start running these spell damage minions, they would run both this and Arcane Explosion. But right now I can't imagine what deck would run this package. The spells are too small for BSM, and burn mage doesn't want to run clears, just burn. Elemental mage maybe?