Just behind the rocks, blowing in the breeze
Monsters everywhere, doing as they please
They try. To. Scare. You!
—Thomas the Tank Engine, Tale of the Brave
In normal stories, heroes often encounter enemies. They may be found guarding some important MacGuffin or perhaps sent to slow the heroes' progress. They are spread out in a few locations where they make sense. In video games however, and RPGs in particular, going from A to B is like carving your way through a thick jungle of flesh.
This is because there are simply monsters Everywhere. There are monsters on the road connecting two cozy peasant villages, in the carrot fields, behind every tree in the forest, under water, in the air and in space. That abandoned tower? Full of monsters. Every single floor. The mine being excavated by poor workers? Inhabited by monsters that attack everything except poor mine workers, because after all everything is trying to kill you, not anyone else.
It doesn't even matter if the The Evil Overlord needs you to make your way to him to do a Hostage for MacGuffin exchange — his henchmen will spawn and brood like cancer everywhere the hero goes, because monsters are a force of nature in the RPG world on par with grass and trees and the existence of sunlight.
This whole thing is obviously for gameplay reasons, to whit, there wouldn't be any otherwise.
You will not find any monsters in small villages however. This is due to an existential dilemma in which monsters need people to terrorize (by standing right outside, roaring).
This trope exists mainly because RPGs Equal Combat.
- Handwaved by the .hack MMO The World and The World R:2 - there's just so many monsters that civilization has condensed itself into cities protected by energy fields or distance ("Root Towns"). Access to this vast wilderness of monsters ("fields") is provided via Chaos Gates which, supposedly, only the players can use. One wonders why it is even necessary since, in a typical moment of Gameplay and Story Segregation, players need to first approach enemy spawn points on fields before either can attack the other.
- Nethack. Horses, bees, trolls, elves, snakes, demons - and everything in between - grows out of rock. Or perhaps they are spawned by the evil Wizard. But why then does he spawn a puny rat to defeat the hero that just killed five dragons without breaking a sweat? Maybe to maintain a certain ambiance? Kitten and Vampire Lord fights side by side!
- In Ancient Domains of Mystery, anyone is an enemy if you attack them (of course), but barring that, only (certain) towns and houses in the wilderness owned by reclusive men are safe areas with no monsters. Heck, even the cities with no random encounters still have monsters; Dwarf Town has the Demented Ratling, Terinyo has Blup the Water Dragon, and all other towns have enemies of some sort. Lawenilothehl and the High Mountain Village are particularly notable in that they have not only random encounters (even in the shop), but also boss fights. And the (random!) boss fight in the latter can, if you're at a low level, kill you with one thrown rock.
- The earlier Final Fantasy games eschew Chest Monsters in favor of having giant enemies somehow living in the boxes. Later games attempt to justify it: Final Fantasy VIII has monsters continuously being born and brought to the planet via the moon, and Final Fantasy X has monsters that are amalgams of vengeful spirits angry at the living.
- Sacred 2 Fallen angel has monsters and bandits on every road, in every forest, and right outside every village. Exacerbated by them respawning almost as quickly as you can kill them. One wonders how any settlements got built in the first place, let alone how anybody manages to travel anywhere with the apparent apocalyptic horde hounding anybody who ventures outside the cities. Kind of gets old when your LV 25 mage is still being attacked by endless waves of rats and kobolds.
- Pokémon, especially in caves. It's even worse in HeartGold and SoulSilver, where more appear if you run, because the noise attracts Pokemon.
- Standard in Diablo II, where anywhere other than the towns will be absolutely swarming with monsters, including the sewers under the town. Justified, since literally all Hell is flooding into the mortal realm and the world is nearing its destruction.
- Golden Sun: Dark Dawn lampshades this during the Grave Eclipse where stronger monsters start appearing. Your party has to escape to a boat and when they arrive, one of your party members will say how they couldn't go five steps without being attacked by monsters.
- Tales of Vesperia actually explains in the backstory that the world is overrun with monsters and most people never leave their hometown because of it. Towns are protected by giant Deflector Shields.
- Justified in several of the Shin Megami Tensei games because the world is experiencing an apocalypse or its immediate fallout caused by the sudden emergence of demons into the human world. Specific sub-series follow or occasionally avert this trope with their own justifications; Persona3 and Persona4 are the most widely known aversions, confining enemy encounters to magical otherworlds where the monsters exist naturally, allowing events in the normal world to carry on largely without issue. Devil Survivor also averts this by confining encounters to either specific plot-important fights, or "free" battles found only at specific locations to help grind and prepare for plot fights.
- Shin Megami Tensei I goes even further with this trope than most RPGs, even the old school ones. There are very few safe zones, less so as the apocalypse worsens. You'll get attacked by demons even just walking around a bar.
- The Elder Scrolls:
- Played straight throughout the series, where it is a staple of gameplay. Simply attempting to travel from one town to the next will see you leaving a trail of monster (or bandit, or necromancer, or vampire, or...) corpses along the way.
- Leads to unintentional hilarity in Oblivion when you realize just how many of the forts, mines, caves, and ruins that are overrun with enemies are located on the ring road surrounding the Imperial City. Despite NPCs warning you to stay on the roads, you'll encounter far fewer enemies by running straight through the wilderness.
- Zig-Zagged in Chrono Trigger. On the one hand, there are no Random Encounters on the overworld, and the zones that do have monsters tend to be wilderness areas or else have thematically appropriate ones (guards in castle dungeons, etc.). On the other hand, the forest which is the only route between Guardia Castle and the rest of the kingdom is infested with monsters. This is a well-traveled route that you will have to traverse over. And over. AND OVER, and the king has access to an army that should be able to wipe the floor with these pests, and yet in four hundred years nobody has bothered to clean them out.
- Sands of Destruction is somewhat infamous for its high encounter rate, thanks in no small part to this trope. A lot of times, it tries to justify the encounters - there are bandits on the roads, wild animals in the forests, and guards in enemy fortresses - but sometimes they simply make no sense: there are no monsters in towns, of course, but the towers which house the Primal Lords are crawling with enemies, despite being located in the middle of town, and despite the fact that it's possible people built these towers for the purpose of worshipping the Primal Lords. Exactly how are the masses going to pay their respects when they get slaughtered two steps inside the door?
- Standard in the Fable games. In Fable I, for example, the road between Albion's two mainland settlements passes through two flavours of The Lost Woods teeming with bandits, Big Creepy-Crawlies, The Fair Folk, colossal trolls, undead, and highly infectious feral werewolves. Despite this, the path is still frequented by Intrepid Merchants who lack NPC Random Encounter Immunity.