system
Given the following post, respond as if you're commenting on Reddit:
human
[General Fantasy] Why do Dwarves seem to have so much trouble holding onto their tunnels?

In numerous rpg universes, dwarven tunnels are infested with goblins or demons or something, (ex Moria, Deeproads, etc) why do the dwarves have so much trouble holding their tunnels?
gpt
Two reasons-

1) Where the dwarves live happens to be where everything the surface world doesn't want to deal with goes to hide.

Think about it. When the surface dwellers drive off some great threat to themselves, where do they drive it to? Into the bowels of the earth. Even dragons have to sleep off their battles with surfacekind under the rock. Worse yet, the truly foul things, the old nasty things, that live *inside* the world have to crawl up through the dwarves to get to the surface where are the softest most delicious creatures live.

2) The Dwarves have all the really good natural resources. What does the surface provide? Wood? Water? There's enough of each for every one. Food? there are enough things crawling the surface to feed everything on and inside it. No, the surface has nothing anyone can't get for themselves just by looking for it. The good stuff, the hardest metals, truthfully, metal *period*, everything shiny, and sparkling and precious, all the darkest and most powerful of magics, all the most hidden of secrets, they're all under the dirt, in the rocks, far down where most things don't or can't go- where the dwarves live.

So, between everything with a brain on the surface wanting everything they live on top of, and with everything below trying to go through them to go live the easy life on the surface, they make a lot of enemies they have no intention of making. They're trapped by fate in a bad place, and almost always suffer for it.

The crazy thing is, in almost every situation, it's the dwarves that *have* to be where they are for the world to work correctly.

It's the dwarves that bring metal and jewels and deep magic to the world, but it's also the dwarves that keep it from being lost. It's the dwarves the keep the things below as the things below, and deny the dark things of the surface a place to hide and fester. 

They also drive the advance of technology in the worlds they're in, usually. Working rock and metal with flesh hands requires some powerful tools, so dwarves become incredible engineers by simple necessity. 

Magic runs like water up top, light and quick, anyone can dip a toe in and find it anywhere if they look. But dwarves, where they find their magic, find it running old, deep, rare but powerful, and it is not to be splashed around like kids playing in a pool. So dwarves learn sturdy ways of using magic, that can handle the power and the potency of what they deal with. Between their powerful magics and their tools, they push forward what can be done on their worlds in amazing ways. 

In the end, they're by default the guardians, the border between a surface world that is young and vulnerable, and a darker, older world full horrors best banished to history.

And yet every time, all these forces hammer against them until they are banished and forced to cower or wander, and their essential roles go undone. The darkness above finds a place to hide and grow strong again, the darkness below extends tendrils into the surface with impunity, and yes, the men and the elves and all the others get their metals and their jewels and their deep magic, and the machines left behind, but they get none of the knowledge, and each generation makes weaker and weaker work of it as they toy at performing works that should be done by the masters.

As usual, some flighty races end up moving as is their wont, whether it to be to less accessible lands or even different realms, and it's the less mobile races that end up having to face the mess left behind and fix it all. And yes, that usually requires coming back to the poor but proud dwarves to make amends and give them back their place in the world.