My example was predicated on the assumption that your game blew up and became popular. And in the example the process of someone watching the video on youtube was that they played the game, couldn't be arsed to unlock all the videos, and just watched them on youtube. You're not promoting much if you're only visible to the people who paid you already.
Regardless, the key point was this:
Does the player even care about these briefings and documents?
If I really want to know what happened in briefing #004, I'll go to youtube.
You made an interesting point yourself:
Did you go to the wiki and read all of the notes from Fallout: New Vegas, or all the books in Oblivion? I sure didn't.
No, but when I was interested in the story of the fallout world, I did indeed go to the wiki. I found a much more distilled version that discarded all the pointless details about test subjects, experiments, government orders, and vault citizens that I wasn't going to read on those green computer monitors anyway. But this side of the argument is worthless: It's easy to prove that something is true for all values of N when N = You. The detailed lore stuff is there for those who care about the detailed lore. But I promise you that of that small demographic, even fewer of them will go through the trouble of getting them all.
You could easily say, "Well that's fine. They don't have to get them. As long as they're interested, and they check it out, that's a plus. Even if they've already paid me, it's more youtube hits if they do search my stuff, and the extra lore was actually looked at." Fine, but now you're talking about generating attention, not improving the gameplay. Leave that to the marketing guys. You're the starving artist. And on the "it should improve gameplay" topic, I've already made my point. No need to beat a dead horse:
If you want to reward the player for playing, reward him/her within the gameplay, not outside of it.
If you disagree, you disagree I guess.
Maybe make watching the videos and reading the documents in game give a skill increase or similar benefit, like the books in The Elder Scrolls or the bobble-heads in Fallout 3? Yeah, I think I'll just do that.
The problem is, the books and bobble heads were the rewards. You went looking for them. You got them. You got the boost. The only time I ever actually had to flip through the goddamn pages of the books in Skyrim was for a quest, or when I thought I might find a quest. But those are two different things: There were books that instantly gave you a stat boost, and couldn't be read; Then there were books that could only be read, and gave you a quest if you read them. In either case, the "reward" at least made appropriate sense. The bobble heads just gave you boosts; they were the reward.
You're trying to combine those into one. Why? One answer: You need to create a reason for the briefings/news clips to actually exist. When the reward only comes after you sit through the extra lore, it becomes the reason to sit through the extra lore, even though the briefing was probably hidden in some hard-to-reach area anyway. Which means they've already earned the reward just by finding it. But it isn't enough that the player found it. They have to let you tell them a story now, too.
All for what? As side-content, it is necessarily irrelevant to the main experience, so why would you make it actually have an effect on the main experience? Cuz?