But, there is no legal mechanism that measures the utility of commercial activities, and which dictates that energy should be consumed only by enterprises that have a certain utility. This is unprecedented territory.
It creates an unregulated, slow, sometimes-anonymous way to transfer USD between parties who distrust one another...
AND
...a vehicle for speculation, not far from gambling.
Basically, it's a way for people to invest in global organized crime and/or speculate about Bitcoin hype.
Does that justify the energy it uses? Not in my opinion, but I don't think its users care.
There's a bigger world outside the island of U.S. There are more political regimes, tax regimes, banking restrictions and all sorts of uncertainty that needs sound and cheaply stored/secured/transferrable money that would protect a person and their family/community against all these issues.
Just the recent multi-trillion debt expansion is a pointer to that. You can't and you won't store your savings in USD-denominated cash. Your options are either getting in debt and tying yourself to a certain credit institution/jurisdiction, or getting some freedom by exiting into Bitcoin.
For people who want to use USD as a replacement for their unreliable local currency, Bitcoin may be one of the easier ways to hold and trade it.
I argue the opposite in a separate comment. The fact that Bitcoin has retained and increased its market value, despite having being inflationary this entire time, demonstrates the value that it brings. I can't tell you where that value is, but if it weren't there, the market would collapse. And it hasn't.
Perhaps 10 years isn't enough for a speculation bubble to burst. But then, at what point would we say that there isn't a bubble? 50 years? 100 years? One might ask the same question about gold since we left the gold standard. Is indefinitely sustainable speculation a bubble at all? Or is that what we call a commodity?
If it's wasted energy, then it's wasted money. But traders don't have unlimited funds. They are somehow generating at least as much wealth as the value of the electricity that is being used.