You don't need to scale supervision on janitors. You can just hire some people and pay them some money. If you can't afford enough supervisors to keep a vague eye on what's going on, live with dirtier buildings or go out of business.
In general I think some things scale well and others don't. Why is it that HN recognizes outsourcing your tech to try and scale fails but other jobs aren't as worthy?
I’d say it’s more accurate that humans have had to rely on trust due to lack of alternatives, but transparency will always be preferred.