system
Given the following post, respond as if you're commenting on Reddit:
human
[Dark Souls] Why don't the NPCs in these settings band together?

Over the game we meet many of them but they are mostly always scattered , going about their quests on their own and more often than not meeting ghastly ends .

Also summons aren't the actual npc but some sort of astral projections if I am not wrong ?
gpt
The phantoms you meet are from the timeline when that person was on their adventure.  All the timelines are twisted and folded on top of each other.  So the people you meet are long dead but also still alive and questing.  It's why you can find them, learns spells and then loot their corpse yet go back to town and trade with them. 

There are tons of groups working together tho.  They are the covenants.