Not a Nix user, but I spent some time trying to understand it. One thing that I wish I would have understood earlier is that "Nix Pills" is a decent, bottom-up Nix tutorial and probably a good place to start. Initially I thought "Nix Pills" was just a collection of recipes ("Nix By Example"), but it is not.
It's not obvious that Turing-complete smart contracts are a good long term decision. I agree that Ethereum is fascinating tech, but with great power comes a great many ways to shoot yourselves in the foot. For financial institutions, being boring is to some degree a feature and not just a bug.
Given that Bitcoin has become quite liquid, there might also be ways to short it. But yes, governments doing it for political reasons would seem like the most obvious incentive.
On top of the argument above, there is also the issue of "chaos" with complex systems. "Chaos" means that small perturbations to the initial state of a complex system can lead to vastly different outcomes ("the butterfly effect"; also found this here via HN the other day: http://www.complexity-explorables.org/explorables/double-tro...).
So in the case of Brexit: the outcome in the cloned universe after 5 years could be very different if the pro-Brexit vote was changed to either 49.9% or 49.99%. It could also be very similar, of course.
If we could have gone to the moon at a fraction of the cost, but people had still insisted on doing it the expensive way, just because the expensive approach came first, that would be a better analogy.