I will (probably) oversimply things, but I see it like that:
Gold linked currencies: someone stores in vaults the value of the circulating money (1) and that "real wealth" is safe to be eventually put again on the market and used for something useful (build microchips, drugs, or something else)
Fiat-currency: someone "prints" money for free (or almost).
Bitcoin: issuing currency costs as much electricity and equipment as the value of the issued BTC (2). Those resources are lost forever.
(1) or a fraction of it
(2) it is an approximation, since the cost of issuing BTC can be more or less than the value of issued coins, but it will not be far from it. If it is very profitable more people will mine, making difficulty increase, if it is hardly or not profitable people will stop mining making difficulty decrease.
Is it correct? Does it mean that bitcoin has burnt some billions of dollar worth of resources?
Did someone address this economical and ethical problem?