My protective rewriting of the Matrix changes the Coppertop battery concept into some kind of handy processor. Perhaps in Matrix II it will be revealled unto the Chosen Dude that the Matrix exists principally to keep all those brains sane so that they can run some kind of processing that is useful to the AI's below the surface. Not that the AI's couldn't do the processing, just that we're a conveniently available and capable of doing the work.
Also, I am not so sure that the Oracle isn't a friendly AI.