I'll repeat what I said in another comment here:

What's valuable is purely subjective. That's what makes markets work. Its also why planning economies from the top down doesn't work. What seems like wasted energy or capital to you is very useful to another person. Many people (myself included) believe that a decentralized, digital, hard money that is tied to the real world through energy is extremely important. So to those people its not a waste of energy, far from it.