And the same goes for dwarves. Caverns look like they're made by something, look how smooth and vast they are. They're dark and mysterious, so we can extrapolate what dwarves are: They're hard workers, since carving out a cave is hard work. They're somewhat stern, since it would take a good dozen dwarves a long time to carve something so elaborate and gigantic. And, of course, they're mysterious and want little to do with humans, since we almost never see them and certainly aren't invited into their homes.
Orcs, goblins, and all of that tie into the civilization vs savagery sort of theme that most games seem to work on. The civilized races are pretty, and friendly, and work together. The ugly guys are mean, and bloodthirsty, and they're too stupid to work together or work on anything other than domination.
|Too ugly to farm?|
Which kind of makes sense. If you've got a race of weak, "pretty" people, they'd have to be good at building walls and buildings and agriculture to get anywhere. If you're strong and hearty and good at battle, you probably don't have much time to build walls and stuff, since your culture is based around warfare, raiding, and constant seiges.
But what doesn't make sense is that despite the fact that even the pseudo-fairy elves have warfare, that orcs and goblins should have agrictulture. Even if we use the classic sense of the extremely Tolkien goblins, what in the hell do they eat when they're just running around caves? Surely there's not enough blind cave fish to feed a whole colony of insane, wretched beasts. Where are their underground mushroom farms? Where are their blind cave cows? Where are their trading routes, to trade with other wretched cave goblins? Everybody has both warfare and agriculture, even the historically insane Assyrians. You know, those guys who used to flay their enemies and put the skins on pillars, and stack human heads in piles hundreds high. Those guys had some regular joes who farmed dirt and forged chains and stuff.
Of course, you could make the argument that since the evil humanoids are nomadic, they don't need agriculture. That's what the Mongolians did, after all. But they also had horses. I don't pretend to be an expert on history, or agriculture, or anything of that sort, but it seems to me that a race of people whose primary habitat is "dark and smelly caves" isn't much of a nomad. Far be it from me to tell you how to run your game of course, but it's an interesting thought experiment.