Treating someone decently and with respect is not a supply/demand equation. Your sentence is why everyone hates us. Are you rude to your waiter because he's on the short end of the supply/demand stick?

> "and choosing which couriers to accept based on how early they arrive for their job interview seems like an excellent metric"

No, not it doesn't. This is cargo cult hiring, no different than hiring programmers based on how well they can reason why manhole covers are round, or why one lightbulb is warmer than the next.

You can determine who is an effective courier and who isn't by having them deliver things. Just like you can determine who is an effective programmer and who isn't by having them write code.

This sort of "hiring by proxy signal even though the primary signal is perfectly testable" is endemic in our industry, and apparently isn't limited to hiring devs.

Tell people what you expect of them, and expect that of them. To do otherwise is shitty mind games no better than the classic Monty Python sketch: https://www.youtube.com/watch?v=zP0sqRMzkwo&feature=kp

> "an excellent metric to use to attempt to differentiate between applicants you otherwise know very little about."

... and we arrive at the core of tech industry idiocy. "We don't have enough information to make a good decision" is answered by "Let's concoct logical-sounding but completely unverified proxy signals to make the decision instead of collecting more information".