Work costs money: like electricity isn't free at the scale of the BTC Network. It costs thousands of dollars of electricity to run those BTC mining rigs to verify the ledger.
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If you're saying the future of "blockchains" is just a cryptographically signed ledger, without any proof of work or BTCs being assigned, I think I can agree with you on that.
But at the moment, "blockchain" is the new cloud. No one really knows what a "blockchain" is anymore, aside from a new electronic ledger of some kind. BTC is clearly a blockchain, but a lot of the "blockchain-based technologies" are nothing like BTC at all.
A lot of these "blockchains" are just centralized banks electronically verifying transactions. Like a notarized bill of sale, except the 'notarized' portion is electronic. Proof of work and all that stuff just don't exist in a lot of the "blockchain" solutions coming out.
What? Do you change all of your savings into stocks or bonds each month?
Currency is the best short-term store of value. And "short term" means anything I plan to use in the next 6 months (My emergency fund will last 6 months without me being forced to touch my bonds or stocks, giving me breathing room for when to liquidate my long-term savings.)
I trust cash to be stable in the short term, even if it loses value long-term. I can't trust BTC as either long-term or even short-term storage.
BTC utterly fails at "6-month" storage due to its volatility. BTC has no history for growing (stocks are based on company profits. So as long as companies are profitable, they'll grow). Bonds are strong guarantees for growing: only bankruptcy can prevent me from getting me money promised through a bond.
What guarantees do I have for long-term BTC storage? Nothing. Absolutely nothing.
Short term? Well, again, stability is more important than gains in the short term (which is why my short-term is cash... not stocks).