Jonathan Deesing penned a blog post for G4TV titled "The Lost Art of the Video Game Manual", in which he writes about the death of game manuals, and how they went from artfully written providers of backstory and instructions to 9-pages booklet when we're lucky enough to get them. Fallout 3 and Fallout: New Vegas both gets mentioned, but weirdly enough there's no mention of the original Fallout's manual.
One of the most enduring features of game manuals is its position as an RPG-aide. Games like Fallout and PokÃ©mon are so large and offer so many features that a booklet can answer simple questions like (Why can't I catch another trainer's PokÃ©mon?) Increasingly though, these questions are more frequently answered on the internet, either on forums or fan-made wikis. There probably isn't a single question about Fallout 3 that can't be answered on The Vault Fallout's own wiki.
I think game companies have taken notice as well. Indeed, in just two years, from Fallout 3 to Fallout: New Vegas, the manual went from a 39-page (Vault Dweller's Survival Guide) to a slimmer (Game Manual.) Even finding locations isn't dependent upon a map anymore. Rockstar's full-sized fold-out maps are intended to help gamers figure out the city, but one can find a map (with all notable points) on the internet in seconds.
It's a dying art, like so many things in video games, but I can't say I don't understand the reasoning. We're paying $60 for a disc and plastic case that cost fractions of a cent, so cutting a few more pennies off cost by cutting down on an unused stack of paper is a good business move. Just ask EA, who recently announced that they were getting rid of all game manuals. And just to feed the hippie-trolls; yes I'm sure that's good for the environment as well. This isn't to imply that I revel losing what was such an intricate part of gaming.