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 people are misinterpreting this. This allows Bethesda to put in more NPCs, making the cities and world feel even more alive. However, it's not going to be like Fallout and it has already been stated as so. All NPCs in the game will still have their own unique names and not be "Generic citizen #349". This dialogue system is much different than what people think. It's not that ALL non-quest NPCs don't have a dialogue tree, there are still plenty of NPCs that aren't quest givers that can talk. The ones that don't have a dialogue tree are the run of the mill citizen walking through the streets. Instead, they all just respond to the choice "rumors". So they won't all just respond the same, they just respond with the "rumor" choice. This isn't really a big difference from the old system. Instead of having "Talk about the city" and "rumors", now they just do rumors. It's nothing like Fallout.
Also, the dialogue system has been going in a much better direction with each game. In Morrowind, every NPC had like 15 options of dialogue but 13 of those 15 where the exact same thing that every other NPC in the game said, which was just terrible. Oblivion had it where there were much fewer dialogue options but there was much more unique dialogue. Also there is more dialogue in Oblivion than Morrowind, just putting that out there. Now in Skyrim, it has as I explained above. They aren't just generic villager X, they are unique people.