Ceasefire is a more expensive and much rarer Whoops that affects all enemy Monkeys. It's mainly used as a counter to Defenders or Temporary Monkeys (especially Robo Monkey and Corvus Academy of Arts). However, most removal and sabotage cards are more cost-effective and/or have additional utility, but only affect a single Monkey and are usually not too expensive that these cards suffer in early mid-game.
Like Whoops, most players will try to use up all their Ammo on Monkeys that attack Bloons, and using Ceasefire on one-delay Monkeys that are not Defenders is pointless.