To me it's less, "why do humans still exist," and more, "why is human society still relatively functional?"I hope they'll go back there and deal with the situation more permanently, a big shame of horror and supernatural stories is that everything end up open ended (and not in a good way, in a 'you only got half the story' way) and you end up with so many 'unstoppable' entities on the lose, the setting stop making sense as to why humans even still exist.
I think so far it's been "fine" in this story because the entities they've come across are all localized to relatively small areas. Like the one in this chapter has been in that village for a while* and erases the existence of the people it catches, so it isn't disrupting modern human society too much.
*Maybe the "land descent" ritual did sorta work? It didn't stop gerai from eating the villagers but it might have stopped it from moving somewhere else.