I think his point in this case is you own the physical item but not the information on it. If not then I could buy some musician’s cd then I could say “Now I own their music” and start selling copies of their cd, publishing it, stealing their rights to it, etc. I think we can all agree that would be bad.
I think it boils down to you need a lot of kids to run a farm due to the manual labor demands. You don’t need a lot of kids to work in a factory or office.