Energy is still somewhat cheap relative to the value of the hardware, so there's been no incentive to optimize for energy usage. This won't change until there's

Energy is still somewhat cheap relative to the value of the hardware, so there's been no incentive to optimize for energy usage. This won't change until there's mass production and the hardware is ubiquitous. You might be right though, but like I said I don't think PoW is necessarily the final state.