I think people are missing that much because the are so "streamlined" to quests... By that, i mean, that they think that the only quests in the game are the ones pointed in your map and in your journal.. but no..
Every cave i go, every ruins, every camps, everywhere i go i try to find some "clues".... I mean to find some Journals or maybe a book... and then i read it, and then this Journal for example, didn't activated any quest, there's nothing on my map or my journal, BUT, i read it, and in it it says that e.g the author of the Journal was scared to go on that road because there are lots of Bandits, and that she/he knew they probably stay in a cave nearby that Road. This didn't activated any questlines or anything like that, and then i go and search for this cave, when i find it, i go inside, kill the bandits, and there is another Journal, this one is from the Leader of this Bandits, i open it, this didn't activated any quests, but i read it and it led to kinda a conspiracy of Bandits for example..
This was just an example, but if you don't do that, you are certainly missing alot of the game.. Because this game is not all about this Marked Quests on your map and your Journal... There's so much things to do and explore, that are really interesting, but just if you don't Limit yourself to the "Marked Quests"...
Been looking for a thread about exactly this but didn't find one but I'm glad I saw your reply here.
Personally I have been extremly dissapointed over the lack of journals/notes that leads to an active quest. It would make exploring so much more interesting to me. I see your point regarding reading them and then trying to decrypt the information. Unfortunately I'm a bit to lazy to do that with all of em, I should however try. Even though, there are still tones of journals/notes in the game that doesn't lead anywhere. Goodbye notes, a bandits last word, a dead npc's diary and so on.
An example:
Spoiler Was out exploring when I stubbled upon a small lake. On a small rock next to it I found neatly folded clothing and jewelry. A few feet away I saw the body of a young girl, filled with Forsworn arrows. Next to her pile of clothes I found a note (her diary) saying how her father had warned her about swimming alone in unstable and dangerous times like this. And how she felt it was all overdone and how nothing would stop her from taking those soothing baths she loved.
After reading that I thought I so wished I could try and find her father to bring him the bad news, I'm sure he is worried sick wondering where she is.
So I agree, you need to interact with the game by decrypting those journals but far far more should lead to active quests. What a great way to add diversity to the game/quests.