Earlier quoted context omitted.
More inefficient than producing and maintaining paper currency? Than mining actual gold? They really are just throwing tons of electricity and hardware at "nothing", but if this kind of activity helps replace the current inefficient systems of currency, then I'm all for it.
The vast majority of fiat currency in circulation isn't in the form of banknotes or coins. (Gold isn't really a currency anymore, so let's ignore that one.) It exists electronically. In a fractional-reserve system, it's also mostly created by its users, but that happens as a by-product of normal economic activity. And it takes a lot less computer work per economic transaction for a fractional-reserve system to create…
The United States alone spends tens of millions of dollars a year on producing pennies - beyond the face value of the pennies.
So the entirety spent on mining bitcoin is not too far off from what one country spends just on minting pennies.