Intra- and inter-cellular biological systems like humans, signalling is effectively PoW. When this is circumvented, you get cancer or other cellular malfunctions. [ ... ] These things are all intertwined with the very nature of entropy and causality and the universe itself, and cannot be circumvented, no matter how warm and fuzzy a "greener" (or more frightful still, "fairer") proof system makes one feel. In fact, any time a non-PoW system is used as if it were a PoW system, it will be less "green" in the long run, although it may deceive cells or people in the short run if they are not immune to the deception.
Very weird conclusion...
But in fact signalling and signal-processing systems, natural and artificial, have always evolved towards using as little energy and matter as possible; and this has often been the most important criterion, more than speed. Thus we have DNA, an information storage system that uses only a dozen atoms per bit; the nerve fiber, that uses much less energy than a copper wire of the same length, and wastes no energy in the form of external electromagnetic fields; and insect pheromones, that can trigger a response miles away with only one or two molecules.
A more energy-efficient solution to achieve a needed goal is an obvious advantage in natural selection, and in a free market as well. For that reason, the
necessary waste of energy and resources called for by the PoW crypto protocols is a serious weakness of the concept.
The mutual recognition of individuals and the creation of trust bonds between them is an innate human trait, older than humans themselves. Getting rid of trusted intermediaries in payments is not a human necessity by itself; it is only a proposed strategy to avoid certain perceived bad consequences of the current intermediaries (banks and governments) under current laws and institutions. If there is a cheaper way to avoid or diminish those bad consequences, without necessarily junking the trusted intermediaries, society will prefer it to PoW distributed cryptos. Ditto if those bad consequences end up being less serious than the cost of the proposed remedy.