right, because there's no other way to prevent modification. no other way. also it's not possible for a single operator to have 51% of the compute in a blockchain.
both of those are obviously false and both have already happened.
blockchain is stupid. it is insanely inefficient, it burns power solely so you can say that you've burned power. it is stupid beyond belief.
51% attacks, on anything at a large scale, are generally more theoretic than practical. The amount of resources you'd need to invest to achieve that on any large currency are astronomical, and you'd need to just completely wreck everything engaging in widescale fraud (which would be a felony, carried out repeatedly and at scale - and likely fairly easy to tie back to you given the massive resource investment to get here in the first place) to try to recoup your losses.
The most probable outcome being a rapid fork and rollback as already with e.g. Ethereum over a relatively negligible amount of money relative to what you'd need to get a 51% on Bitcoin. You'd likely end up losing a massive amount of money, as well as look at possibly spending the rest of your life in prison. So the only real purpose in doing so is for attention or trolling, but the costs involved generally preclude this motivation.
Hard focus on one use case, albeit most famous and has some properties you mention.
There are other use cases, like it or not. And its popularity - don't blame tools for basic human greed they only allow to be manifested, that's not a smart approach to get anywhere apart from endless complaints how this and that sucks.
how do banks do it now? you know the answer, at a high level. it's the same way we prevent unauthorized access when the blockchain isn't involved, and it's how we prevented unauthorized access before the blockchain existed.
it's how banks prevent someone from withdrawing money from your account without your permission, everywhere across the entire globe at once, all the time.
it's the same reason that I, a normal user, can't delete people from active directory at work, or change their passwords to mess with them.
you've dealt with this kind of permission system your entire computer-using life. you know how it works. you know what it is. being distributed doesn't matter at all.
Blockchain isn't just distributed, it's decentralized and trustless.
We live in a time where any form of centralized authority is increasingly abused. Blockchain prevents this. It also prevents incompetence as we also live in a time where centralized data and credentials are regularly leaked or hacked with no recourse available.
how do you not know this? think about that. think really hard. you can do it. how do people prevent unauthorized access when the blockchain isn't involved, or before blockchains existed? really, really think. you know the answer.
If you don’t already know how simple permissions, read-only storage, and digital signatures work, I don’t think that you have any business telling anyone that they’re misunderstanding anything.
Bitcoin was made to solve problems that exist only in the minds of those who wish to make money with bitcoin. Other blockchains serve the same purpose. Zero people use it as a ledger, except as a joke or to prove how stupidly limited and inefficient it is.
Bitcoin also has created problems that didn’t exist prior to the invention of the blockchain.
So, aside from the myriad negative effects of the blockchain, it is wholly and completely pointless unless you think it will make you money. If that’s how you think of yourself, you are a parasitic scammer spreading ransomware trying to make people think you are a legitimate human person with a right to live.
both of those are obviously false and both have already happened.
blockchain is stupid. it is insanely inefficient, it burns power solely so you can say that you've burned power. it is stupid beyond belief.