The Truth About Van Halen and Those Brown M&Ms (2012)
npr.org
npr.org
They still had to deal with the heterogeneous set of arenas that existed around the country and to do so, they laid their requirements very carefully in a contract - important things like how much weight the stage had to be able to take. But how to tell immediately whether someone had read the contract in detail when they arrived as a given venue? Ah, put a random but visible requirement right in the middle of the contract.
I heard about the "why" for this years ago (of course, the article is from 2012). Pretty sure I'd heard the reason considerably earlier that.
That phrase just distills down to 'verify'.
Or more generously 'verify and extrapolate' but it still lacks trust.
If I don't trust you, I don't even speak to you. I don't buy a sandwich from you, I don't buy a car from you, I don't fly planes over your territory without mach 3 interceptor escorts armed to the teeth.
If I trust you, but double check you, I buy the sandwich, but I don't leave the counter without opening up the bag, unwrapping the paper and checking for onions. I buy the car, but have a third party mechanic inspect it. I fly the plane through the territory, but also observe from orbital satellites, just in case.