And humans malfunction pretty badly without input. Even solitary confinement quickly drives them insane.

Yes, but that's the fundamental difference. Even if I closed my eyes, plugged my ears and nose and laid in a saltwater floating chamber, my brain will always generate new input / noise.

(GPT) Models toggle between a state of existence when queried and ceasing to exist when not.

You could just let the GPT run in a loop and it too would continue to generate tokens.