Dungeons - What Are They Good For?

In heroic fantasy adventuring, there seem to be two broad schools of thought:

1. Dungeons are a perfectly viable environment for exciting and rewarding adventures.
2. Dungeons are dumb.

Both make sense to me.

My own campaign setting goes a long way to embrace fantastic realism and some semblance of verisimilitude. Sure, there's magic and dragons and stuff, but at least it pretends to make sense. For some reason, dungeon environments can be harder to get players to swallow.

The Avremier (and many others) setting offers the following general reasons for why a dungeon may exist. Having a purpose also helps with writing a dungeon and having it seem real in any way whatsoever. These ideas are presented in no particular order and make no claim to originality or unique brilliance. They are just ideas.

1.      Living Space: Possibly entire ecologies or civilizations. By choice or necessity.

2.      Burial: Tomb or catacomb. A place for the dead and/or undead.

3.      Worship: Some temples or shrines are hidden from prying eyes. Some deities just prefer the dark.

4.      Internment: Locking someone or something away.

5.      Defense: Can be more secure than a castle or fortress.

6.      Isolation: If the surface becomes unbearable or undesirable, one way to go is down. A viable means of riding out many forms of catastrophe.

7.      Mad Obsession: Sometimes the voices just demand a crazy underground labyrinth.

8.      Mine: Digging for precious substances tends to leave behind passages and chambers.

9.      Natural Caves: The original fixer-upper.

10.  Planar Cyst: Part of another dimension intrudes upon this one.

11.  Actual Dungeon: Place of torment and despair.

12.  Actual Underworld: Like some weird mythic afterlife.