The original plot of the movie was that humans were not an energy source but the computing substrate; that all those brains were networked together as a meat-based platform for the AIs to run on, which is why Neo was able to change reality in the Matrix, because he was able to override the programming for the chunk running on him at any given time, just by thinking it.

But the fucking mouthbreathers they got in for their focus groups didn’t get the concept, so they had to rewrite it, demoting humans to freaking lemon-batteries and making a mockery of the whole thing.

Yes I’m bitter.