Because Cain operated on a singular basis. Anything he knew was up to his own discretion on whether to disseminate to other parties at his own discretion and currently his discretion said that the Yates twins were being needlessly kept in the dark. It was hard to reconcile his solo ways (with occasional assist from his children, granted) with Abel's more structured environment for dealing with threats like these.

"Sounds a lot like regular old house arrest to me," Cain said with a furrowed brow. "There's keeping them out of the loop... then there's not even letting them know a loop exists. Besides, if they don't know much about you then they're more likely to hinder you at every turn than let you do your work. Isn't it more efficient this way?" He raised a hand before Abel could say he was avoiding part of the subject. "Believe me, I really do think they should know where we stand on the Death Erasers, but I'm following your lead here. I won't tell them, but it's too late for you. You're welcome."