1. What's the in game universes reason for there being so many (abandoned) dungeons in the world...

1. What's the in game universes reason for there being so many (abandoned) dungeons in the world? So many that you can make a living raiding them.

2. How do we make dungeons a thing IRL?

1- In D&D a lot of the dungeons are natural caves or abandoned "regular" buildings/settlements. Sometimes they aren't abandoned, and you gotta fight their regular inhabitants.

2- Staff some buildings with interesting layout full of armed goons, loot, and tell them to shoot on sight.

If you consider abandoned buildings dungeons, they already exist. Especially industrial ones.

Traps in form of environmental danger (exposure to toxic shit of all varieties, weakened floors due to moisture damage, all kinds of things to snag on)

Potential guards in form of cops if you're trespassing, or junkies.

Treasure in form of shit that hasn't been stolen yet, copper wires.

>1
D&D is essentially a fantasy setting with a few apocalyptic events and fallen empires. Supposedly Giants were the first civilization then the other races like elves and dwarves started becoming more active after the giants and dragon war nearly made both giants and dragons whiped out. I can't remember exactly why the dwarves and Elves went into decline but by the time humans are starting to form their own kingdoms and empires there are loads of ruins for them to go explore and most of the powerful magic items are from an age lost past.

So essentially D&D is kind of a post apocalyptic game set in a fantasy setting.

>2
There were a few but the days of being an adventurer died fairly recently in the 1900s.

You want to do something cool but possibly dangerous but the omniscient gods are always snitching on you to greedy adventurers who want your stuff. You gotta go somewhere isolated, defended, populated by self-sufficient security and complex enough that those idiot adventurers are too busy messing with goblins and strategically placed ruby-eyed idols to interfere with your succubus summoning ritual.

that image is simultaneously giant and pathetically small.

>Supposedly Giants were the first civilization then the other races like elves and dwarves started becoming more active after the giants and dragon war nearly made both giants and dragons whiped out.

[citation needed]

It is the natural tendency for good to rise and evil to sink Any large underground space, regardless of original intention, is at risk to becoming home to evil things, seeking shelter from the surface or crawling up from further below as the residual Good of its making fades.

Adventurers do more than simply slay monsters, they bring that same power of goodness back into the dungeons with them, purging and purifying them for a time. But in time, the Goodness ascends once again while Evil falls, the cycle ever-repeating since the dawn of time.

>1. What's the in game universes reason for there being so many (abandoned) dungeons in the world? So many that you can make a living raiding them.
They aren't abandoned almost all of the time. Even from 1st edition, the "dungeons" are populated zone filled with dangers and inhabitants. My group campaigns rarely go into ruins except for artifact hunt and those are rare.
Do you even play tabletop?

>2. How do we make dungeons a thing IRL?
Already happened.
Look up abandoned buildings filled with dangerous drug addicts and gangsters.
Outside of urban areas, there are abandoned villages and factories used by organized crime as drop sites so you might die and disappeared if you are caught there at the wrong time.

The world is infested with Mountain Maggots.

Volos Guide

1. There arn't that many, but the ones that are are packed full of goods. You basically only have to enter one dungeon per month, and risk your fucking life. It's not a big industry, because not many people are big on being mercenaries.

Torchbearer is set after civilization expanded into the wilderness, and then has been pushed back to much smaller enclaves, with the ruins of what was built left behind.

Local evil god likes to test and/or kill people, so he makes dungeons filled with traps and monsters for folks to wander into. He also puts treasure there to play off greed and to lure people deeper. His minions also tend to expand the things downward to try and breach the underworld and let evil flow into the world above.

Current Explanation given for D&D 5e.

Which reminds me; what IS the default setting of 5e? A lot of the monster lore doesn't seem to match up with Forgotten Realms, and the adventure modules talk about how you can best tied them into a bunch of other settings.

General ideas for "realistic" dungeons:

1. Tomb Complexes. Things like the pyramids, valley of the kings, etc. Lots of treasure, probable location for undead.

2. Sewer systems. Located beneath large cities, either ancient or recent. Not much treasure, except from what's thrown away, but easy to reach. Full of pest, vermin, and those who can't live on the surface.

3. Mines. Generally abandoned. Treasure will be raw materials, monsters will be other people scavenging for the same materials. Not as many traps, but plenty of hazards such as firedamp.

4. Undercities. Either widened natural caverns, or some great feat of excavation, these are settlements entirely built below ground, often dug into a mountain or similar. If you're hostile to the inhabitants, or if it's abandoned, these make excellent dungeons.

Many cities will have some combination of these beneath them. Some places, such as Paris, have such severe tunnelling that they have all four.

Been a thing since AD&D.

A super-advanced race has left the flooding planet, leaving engineered descendant race behind. "Dungeons" are really their cities and bases, some with life support systems still functioning.

They're built by dungeon masters in order to attract monsters to them and away from the countryside.

I like making the Underworld a legit thing. Hell is actually deep below the ground, so is the land of the dead, so shit tries to come up, and beings try to dig down.

It just happens.

Our Pathfinder party basically made a dungeon when we used magic to create a fort carved into a mountian, with many different rooms, flaming skulls as decoration, etc.
Now we're abandoning it in favour of a flying fortress in the orbit of Golarion, which means that our fort will be vacant and probably some monsters are going to move in and turn it into a dungeon over the course of decades or centuries.

sustainable adventuring.

We did live there for a few months, and expanded it a few times to accomodate some NPCs.

They're holes in the ground that fill up with treasure and monsters because they were cleaned out and then abandoned by a group of adventurers. They get more monsters who bring in others to guard their shit or keep as pets, and get filled with magic items from the rich, dumb adventurers who get killed until a bad enough set of dudes can clear it again, or the inhabitants become so numerous and such a threat they strike out an invade he nearest hub of civilization.

...

Elminster restocks them full of treasure every time they get looted.