because Undertale doesn't show the possibilities of what could happen to a complex civilisation being trapped under a spell for centuries in a limited space with non-naturally growing resources and no actual weather cycle.....???
D'OH!
not to mention, as I said before, petal's attention to detail. maybe you should mind your business if you're gonna be this slow..
undertale does addresses this point though, which is why magic is a thing. We see in the original game about the monster's dreams of going to the surface, and how they build their civilization around it
Horrortale is about how it would happen if magic didn't exist but at that point it's not the same universe anymore, they become just like every other evil fantasy race.
