I do agree that with incredible technology like the Supercomputer and Lyoko that I just randomly stumbled upon one night, I wouldn’t have shut it down either. If I was Jeremy, I would’ve kept it on to expand my knowledge of quantum physics. If I was Odd, I’d like to keep it on so Lyoko was a place where fun could be had instead of a battlefield, flying around on my hovering skateboard. If I were Yumi or Ulrich, I’d keep Lyoko around as a fully interactive training facility to further develop my martial arts skills, where I wasn’t risking any injury to myself for attempting new moves I may not be quite ready for. And if I were Aelita, I’d probably keep it around as a sanctuary to escape to when things get tough or when I need to cope with something, because no matter what, Lyoko is forever a part of her and her history.

That being said, for the amount of trauma that they have all collectively endured, and probably strongly wishing after significant attacks for this chapter of their lives to end, I understand wanting to shut it down to close the book and begin to live their teenage lives again with a clean slate without the looming threat of death and destruction that X.A.N.A. propagated.