>>718395509
They literally never plugged any scientist by choice.
Ruvik made the machine and was the only one who fully comprehended how it worked at the time so he made it so it can only work with him in the system to cuck the not-Illuminati, which decided to instead extract his brain for now while looking for an alternative solution when he was uncooperative and making more trouble than he was worth.
Which was also fine since nobody important was intentionally put into the machine.

The only other non-disposable person connected was the scientist guy from the story, except he caused the game's events and plugged himself alongside Leslie out of desperation since not-Illuminati was looking to get rid of him too, and Leslie was the important person for the not-Illuminati since he could be a potential replacement for Ruvik's brain and the only card the scientist guy had left.
In fact, they were desperately trying to find replacement for Ruvik since they didn't expect him to be able to be conscious but instead he was fucking up the whole system.

tl;dr not a single scientist or anyone non-disposable was ever plugged to the machine by choice, Ruvik was causing trouble, scientist guy did it himself because he was cornered and Kidman was intentionally disposable.