Jeskai Ephemerate runs Counterspell, Mulldrifter, Archaeomancer, and Murmuring Mystic all in blue, making Red Elemental Blast excellent to counter a key spell or destroy a resolved blue permanent like Murmuring Mystic. Bitter Reunion's looting is less valuable than direct interaction against a deck full of card-advantage engines you need to answer. Keep Thraben Charm to pick off Augur of Bolas, Murmuring Mystic's bird tokens, or an Ephemerate target, and Lightning Bolt remains strong against their small creatures.