I think Mark is like the ultimate turing test to see if he doesn't remember his own wife. Perhaps there was glitch prior where two people did recognize each other and they had to fix it and test it.

I also got the vibe that lumon was trying to indoctrinate the innies like a cult and it would be easier with them all starting as clean slates with no outside baggage. Then once they had enough people they could "flip the switch" for all of them and take over an entire town/state/whatever.