Its like gambling, that's why.

Just buy hoards of precut diamonds, why waste effort digging???

This is a common logical fallacy known as the sunk cost fallacy

isn't this obvious?

this picture does not repressent at all how the world works. (most if not all "deep" illustrations out there do not repressent reality at all).

that person has no way of knowing if the diamonds even exist there or if he is digging in the proper direction.

even if something exists there that person has no way of knowing if that is diamonds or some pile of garbage.