They are. Just like Pathfinder, you can just create a character using the normal character rules, and use that as an NPC.
You do not need traps to play D&D.
You do not need magic items to play D&D, and specifically with 5e they are intentionally taken out of the assumptions for character advancement. Magic items are rare, other than the few already in the players document (healing potion, mithril chain, dragonskin armor, a few other things like that), and it's assumed one play style includes no magic items.
Both of these are no longer like they were in 3e and 4e. There is no expectation of treasure of any kind built in to character advancement (just like magic items). The DM is free to hand out whatever sums they think are appropriate, and all the types of coins and gems and such are in the PHB. There is some "fluff" advice, but it's not the "rules" and you don't need it to play the game (and it's really just random tables that it explicitly says don't have to be followed).
As for encounter building, it's very much left up to the DM. There is some "fluff" advice, but it's not the "rules", and you don't need it to play the game.
You ONLY need the PHB of 5e to play the game, given the standards you've applied. If the NPCs-only standard is a fair standard in your opinion (and I am assuming it is for this argument), then by that standard you really only need the PHB to play 5e. None of the DM stuff and Monster stuff is "necessary" to play the game. The DM can create a campaign using just the PHB, NPCs created using the PHB, and the standard skill checks and combat rules in the PHB. There's more than enough in the Player's book to run everything you need to play the game, if NPCs-Only is what you want to do with the game.