I think the big difference is that it's not a direct replacement - it feeds off of the existing people while making it much harder for them to make a living. I

I think the big difference is that it's not a direct replacement - it feeds off of the existing people while making it much harder for them to make a living. It would be as if instead of cars running on gasoline, they ran on chopped up horseflesh. Not good for the horses, and not sustainable in the long term.