Ah I understand the OP, and I agree. You could tell right away if an NPC is involved in a quest because if you cant initiate dialog theyre just 'Red Shirt', or simply by their name "Random Townsperson 01".
In Oblivion even Guards had the dialog menu. Random people still had an actual name, and you could still talk to them even if it was just "Gossip" you wouldnt know right away if theyre important or not because quest dialog pops up when the quest is active.
New Vegas did away with relatively useless generic topics but I dont think it worked well(and I liked NV far more than FO3 for the most part).
I think this new system is a step in the right direction. Instead of...
"Mudcrabs are nasty little creatures aren't they..."
"Hello"
"Hello"
"There's trouble in the land of the elves"
*Clears throat*
We can expect Radiant AI to start building "idle" conversations based upon very specific criteria... While you might not be able to talk to some people directly, their idle conversations will make sense... and you'll be able to overhear quest information in public.
People (Even people who normally cannot be talked with) will start to interact with you based upon programming (Their relation to you, or someone you've interacted with) and might even approach you with dialog if you trigger it.
Also, you could essentially triple (Or more) the number of NPCs in cities. The most beautiful part of all this is that once these systems are in place, the Bethesda developers can still hand-craft just as many (if not more) quest lines as there were in Oblivion! While allowing systemic quests to be triggered by player actions, "Activating" the once quiet NPCs.
The amount of content will be busting at the seams! We're starting to see the future here, guys.