But wouldn't it be even better if the farmer bought the tractor on a loan? Now the farmer keeps the entirety of his production and the guy that would have rented the tractor also has to work, further improving society.
From the perspective of the banker/lender, they're still living off someone else's labor (which is fine for me since it's the result of a voluntary exchange for something else of value, but it seems like it's not for some upthread posters).