But what is it actually used for?

Okay, you can donate to WikiLeaks ... But probably 99.999% of people who have possessed cryptocurrency are just speculators: buy low, sell high. And ironically, the exchanges are centralized entities :p

Bitcoin in particular is used as a store of value, or a form of "digital gold".

Everything is speculation (you hope it goes up in the future, but no one knows for sure), but large corporations are increasingly keeping a balance in Bitcoin, as are wealthy individuals and fund managers.

To understand its place in the world, you need to be a bit more familiar with government bond yield and risks, money creation/monetary policy, the macroeconomics of perpetually rising debt and negative interest rates.

Gold has a $11 trillion market cap, and its not because of industrial use or because it sells well as jewelry.

You got brainwashed into believing this by Reddit. Back in 2017 when Bitcoin was utterly crippled in usability and scalability, the centralized forums upon which information was flowing were seized by bad actors and used to manufacture this narrative. Bitcoin was intended to be peer to peer money, not digital gold.

Peer to peer money (low transaction cost, high scalability) is not immediately possible without tradeoffs to decentralization.

You can increase block sizes to a degree, but that threatens decentralization by making it difficult/expensive for nodes to sync and store the chain.

We have an experiment called Bitcoin Cash and endless other forks promising low fees, but adoption has not followed.

Indeed, when you depend on a package from a Nix channel, you implicitly depend always on the latest definition of that package in that channel.

When the version matters, Nix has separate packages for separate versions. There are separate Nix packages for Python 2.7, 3.7, 3.8, 3.9 or 3.10, and there's OpenJDK 8, 11 and 17, etc.

You probably don't want to depend on an overly specific version anyway. If a security fix for one of your dependencies is released, you want it. Furthermore, CI ensures that everything within a channel is maximally consistent.

Someone is always going to want to run some piece of legacy software with legacy dependencies. The great thing about Nix is that it allows you to 'install' very specific versions packages 'locally' (in a shell) without polluting your entire system.

I also cannot understand how a paper whose main contribution is a set of benchmarks, does not actually make the source code to those benchmarks publicly available. Unbelievable that such a paper can pass peer review. Very unscientific.