Well if this shepherd didn't know anything about the mining industry, what about owning property?
He could have bought the mineral rights to the land, have a survey taken, realize there are billions in diamonds in them's hills, and have complete control of the entire mining operation and its profits.
Notre sure if the example is relevant, as I'm largely basing it on US law. But your argument doesn't really stand as an excuse to tell someone else.
FWIW, the entire example is flawed. Erasmus was 15 years old and he found the diamond under a tree.
NASDAQ:FB?
But seriously, if you stumble into a diamond mind worth a couple billion that does all the work for itself maybe you can find a way to keep all that money to yourself. But I'm willing to bet you're talking about 1% cases here, not the standard type of story that is brought up on HN.