I would argue that there is potentially a use case when it comes to things that can be completely represented digitally e.g. money.
You say that, and then look at the number of companies selling blockchain based services promising exactly that, and enterprises paying for projects...
It's understandable why as well. Pure "digital world" businesses that blockchain can deliver like provably actuarially fair gambling exist, but they're pretty niche.
I'd question whether money can be completely represented without recourse to the outside world - what gives money relatively stable value is the real world enforcement of contracts, debt obligations and taxes. Take those away and whilst your blockchain can validate the integrity of some numbers you hold, you can't guarantee anyone actually exchanges it for anything actually useful in future.
From my understanding, blockchain is essentially "cheap trust" . You can pay the system a fee to trust math rather than a human. Once I learned that, I realized there are very few scenarios where cheap trust is needed.
So perhaps I should adjust my first statement with "people who understand blockchain" - although even that's not necessarily fair as it assumes that I "understand" it.
I suppose what I'm getting at is that I think it's unfair to look at the number of scammers/people selling "blockchain" services and make an assumption on the industry as a whole. Most of the developers in the space that I know completely write off those people and don't even consider them in the industry.
On whether money can be completely represented without recourse to the outside world -> Agreed, I should again amend my statement to say "value". There is no doubt that 1 Bitcoin represents a certain amount of "value" right now and that value has so far proven to be un-censorable. Whether it will be successful money is a different question.
The comment above says that the blockchain provides a satisfactory answer to enforcement of contracts. People really do seem to think that contracts made on the blockchain will magically enforce themselves in the real world.
The contracts don't, and can't, concern themselves with anything that is off the blockchain. Once the ether is in your account, the contract is complete.
As an example, fradulent fish is a huge problem in the fisheries and food industry. At every step of the supply chain, there is temptation to substitute expensive for cheap fish. Most Chilean sea bass you buy isn't actually Chilean sea bass, for example.
A lot of people are hyping blockchain as a solution to this serious problem, not appreciating the fact that the technology cannot actually tell different types of whitefish apart. I really would like a solid counterexample where blockchain actually would help, but I've never heard one.
But it still adds new problems. Electricity use, the irrecoverability of data/auth if you lose a key, the inability to erase problematic data.
1. On Electricity - It needs to be expensive to try to cheat or steal from the system. Currently with gold you would need to hire a private army to steal from and break into vaults - that's so expensive and crazy that I don't think most people are willing to undertake that risk. Currently I think electricity is the best way to make digital native things expensive. I'm not sold on anything else yet (definitely open to new solutions, but I'm not convinced think PoS is a viable one).
2-3. I think this is an interesting tradeoff. The way I look at it you pick 1 of 2. Either you trust someone or some people to return lost funds/remove "problematic" data or you trust the system in which case those things can never be recovered/removed.
I think calling those "problems" might be premature as they could actually be "benefits" depending on how you look at them.
Re 2-3: Tell that to customers of Quadriga and MtGox and the countless scammed, those who paid ransom to kidnappers. Everyone who lost their keys. It's a problem, let's face some reality here.
No, not people in the sense of end user customers. The industry is selling snake oil and some investors have bought into it and subsequently promote it.
10 years down the road and they're still trying to find a mainstream use case, but they won't find it because in the end using a blockchain makes everything harder if you are a legal enterprise.