Basically a way to limit or prevent Monarchs spawning additional Cutieflys. Main reason is because they can be farmed infinitely, which may not be wanted when using mods like SellBodies. It also means Cutieflys/Monarchs cannot be "dealt with" like most other enemies (Killed, Trapped, led away) as they cannot be trapped or baited somewhere to not cause issues, leaving killing as the only other option, which doesn't work since they create an infinite loop of spawning each other.
Bonus, is that it would also fix the incompat issue with FairAI where quicksand can kill them over and over and spam.