Or, much shorter reply than my other one: when I was a kid my mother took me to the public library which was a bit away so we took the streetcar. Passengers entered and bought tickets from the tram driver, so I asked my mom, can the driver keep the money he's getting? I found it highly unjustified and unjust he has to turn over the money when his work is done. After all, Labor is entitled to all it produces.