User blog comment:Beast of burden/BIOSHOCK 3: BIG BROTHER/@comment-6024608-20131019121029

They already said that only Little Sisters could produce the ADAM  properly (so that isnt the reason to implant them).

But there could be an even more sinister reason for implanting them -- like LS they could still have the  regeneration ability --- useful for when their skulls are opened to take the nerve tissues used to make the bioelectronic circuitry used for The Thinker...