What do you think needs more energy: several systems (2, with some intermediaries) that talk to each other, one decrementing a number in a bank account, and another incrementing a number in another bank account, vs. thousands of systems that compete with each other trying to find some hash the fastest by guessing?

Both need to talk to each other over the network, but in the second, it's thousands of systems needing to synchronize the information.

What a stupid lie you're telling yourself to justify that "this is fine!".