"Proof of" is a euphemism for "waste of resources" in general.
In real world finance a common stock is proof of making a useful investment at some point in the past, when the stock certificate was issued in return for capital. Same with other tradeable and non-tradeable assets.
The crypto version of proof is closer to a bearer bond or a bar of gold: whoever has possession has possession.
In cargo cults it would be like complaining that the control tower made of wood has the wrong number of windows, all the while missing the fact that you don't have any aircraft.