I will admit though, it being from Determinate Systems makes me wonder why they built it. They're not some hobbyists, they're a company built around making Nix tooling - and one of their most publicized tools, the Determinate Nix Installer, is actually a tool that, obviously, overlaps with existing tools, but has a very clearly stated objective and reason to exist. It seems very likely to me that there is, in fact, a reason for why they built this. If I had to guess, it's probably meant to be simpler, more robust, more elegant, etc. but I'd love to hear about it.
Unfortunately, unlike many of their projects, they don't seem to have a blog post yet for it.
I mean, at the very least, I do this because I make/release things because there's a gap to fill or an itch to scratch. And if I'm releasing something it's because I'm hoping it will be useful to others.
It seems like a natural conclusion to spend a fraction of the energy to author, to detail it's reason to exist.
Anyway, no one owes me anything but I trust that Determinate Systems has a grander vision than I can see, I just want to be clued in, to be honest ;).
Unfortunately, unlike many of their projects, they don't seem to have a blog post yet for it.