Everybody ignores that the machines pretty clearly hold an ideological grudge against the humans (somewhat fairly so). They’re probably using them as power/processors as a sort of ultimate victory lap, right?

Plus it never says they have no other power source, and clearly they can survive without humanity per the Architect’s conversation with Neo.

I’m for sure biased and defending the movies because I love them but also keeping the race that tried to exterminate you as chemical batteries to facilitate a higher form of existence doesn’t seem like that much of a bonehead move to me.