It's explained early on in the story, though it can still be confusing for anyone who hasn't read it yet, or who is trying to relate it to our own reality.
Yeah lol some people have difficulty of suspension of disbelief in sci-fi/fantasy genres, it is always the best way to enjoy those stories as well an alternate reality like eruption imminent, but maybe those people love to be miserable over fiction lmao.
To fully enjoy it we have to disregard some rules of our present society and immerse in an alternate one where the rules are set by the author/dev, of course they live in our own society and is hard to let go of everything that exists presently.