So, in a sense its value indeed derives directly from the work put into the system. Which is not to say there aren't alternatives (I'm really curious how Proof of Stake will change the Crypto landscape), but at least for BTC, that's how it is currently.
Point being, trust and trust-worthiness are two separate things. Most people investing in Bitcoin have not in any way confirmed for themselves that the algorithm is trust-worthy, they just trust that others are also willing to buy it so that they won't be left defrauded. Hell, people have been defrauded by the likes of Mt Gox, and the network didn't collapse entirely.
But there's also the people that invest long-term because they think crypto currencies have a lot of potential to be adopted more widely in the future, which entirely depends on their trustworthiness. Without that second group, any sufficiently negative news would cause the BTC price to collapse completely -- and to be fair, there's always the risk of that happening (Tether sends its regards), but the underlying "trust in the benefits of the system itself" at least gives a floor for its price that's above $0.
Ethereum has done it this way: First you build a stable blockchain, secured through tremendous amounts of power. Then, once your system has been widely adopted and people have "skin in the game", you switch to Proof of Stake to minimize power consumption while still maintaining security.
PoS is the better solution, environmentally speaking, but it necessarily depends on there already being value in the system that people can be held accountable with and thus kept honest. But to reach that state, people have to trust your system first, and if you're not an already trusted entity, PoW is one way of achieving that initial phase of trust building.
I'm sure you don't want that though, because solar+batteries will power interplanetary civilizations somehow.
The energy isnt wasted though, the safety of the trustless transaction is proportional to the expended energy. While not the source of value, it is a necessity, not a waste.
This would be somewhat true if Bitcoin were the only mechanism for trustless transactions, but there are others that consume far less energy, such as https://en.wikipedia.org/wiki/Hawala.
What's also maddening is how subjective the term 'value' has on it's intended usecase that some can be so completely oblviius to make coax it into a specific farmework: cocoa beans and shells were also equally valuable to it's respective communities, but your forcing of modernity to this matter is equally marred by illogical and quite frankly lazy conclusions.
Bitcoin (lower case b, as in the token) does require a great deal of hashing power, but this model, proof of work, is what is required to ensure Bitcoin's immutability (the network capital B). And that is the cost of such a system which, if you aren't aware, is mainly operating on renewable energy [0].
That is just the cost of entry if you want to incentivize keep everyone honest and play by the rules, the fiat World is littered with countless stories of failed currencies and failed societies and cultures because man's inherit nature: greed and corruption.
0: https://bitcoinmagazine.com/articles/study-74-percent-of-bit...
And to make it difficult to forge transactions it asks you provably(!) burn some electricity.
The point of "Marxist" labor theory, is that you shouldn't pay workers less, than the value of what they produce. I don't think Bitcoin miners ever made that claim, unionized and found their class consciousness to get paid the real value...
No! No it isn't! Gah! I'm sorry but it is so frustrating to hear this nonsense repeated over and over. Bitcoin is not valuable just because you wasted shedloads of energy to make a bitcoin! It's valuable because somebody else will exchange something of value for it.
It's incredibly maddening how so many crypto-libertarians suddenly turn into believers in some Marxist "labor theory of value"[0] when you press them on bitcoin's incredibly wasteful Red Queen's race[1] of ever-escalating wasted energy.
[0] https://en.wikipedia.org/wiki/Labor_theory_of_value
[1] https://en.wikipedia.org/wiki/Red_Queen%27s_race