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.
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.