
Continuity mistake: When the T-1000 walks past the deactivated T-800 just after being shot at by Kyle Reese, you can see that the T-800 has taken a lot of damage to the face and the nose is missing. Once the T-800 gets up after being reactivated you can see that the nose is back with a lot less damage to the face with a close up shot.
Chosen answer: As long as Skynet kept sending other Terminators into the past to kill John Connor before he became the leader of the human resistance, it was necessary to keep sending reprogrammed Terminators into the past as well so that the timeline would not be altered, thus resulting in a Skynet victory. While it is possible that John and the resistance may have used reprogrammed Terminators to help them in the future, this was never depicted or otherwise mentioned within the film series.
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