Izzet Prowess is a fast, low-to-the-ground aggro-tempo deck that wants to race; Vexing Bauble shuts off their free Mutagenic Growth and taxes their cheap cantrips like Preordain, which is a huge tempo gain. Surgical Extraction can strip a key Dragon's Rage Channeler or Cori-Steel Cutter after it hits the graveyard/battlefield to blunt their engine. Claim the Firstborn steals a cheap threat like Monastery Swiftspear or Slickshot Show-Off to turn a blocker into extra offense. Ox of Agonas and Nethergoyf are cut since they're clunky against a deck this fast and low-impact for their mana; Raucous Theater's tapped land is too slow in a race.