The entire point is that it wastes something. Not specifically energy. The idea is that there is a sunk, unrecoverable cost associated with mining. That cost ma

The entire point is that it wastes something. Not specifically energy. The idea is that there is a sunk, unrecoverable cost associated with mining. That cost may be able to take other forms, though. In the case of proof-of-stake, that cost is the time-value of money.