As far as I understand this, by "personal level" you mean that the DM is playing the NPCs and the players the PCs, is this correct? If yes, then this is not what I am talking about. I am not talking about the simple fact that the DM (and not the players) chooses to make all rolls for his NPCs. I am talking about the players influencing the outcome of the conflict through the use of their PCs abilities (the obvious being social skills, but maybe the use of force as well or other things). Now, there are situations in which PCs cannot influence the outcomes of NPC/NPC-conflicts.
But again, the question remains why a die roll is necessary to find out a plausible or believable result on a DM table. The roll could end up with any result on that table so why not just pick one without rolling? Why not mak something up on the fly that fits the development and the reactions of the PCs in this particular situation best? Why the need for more mechanics and tables, preptime and dicerolls when a narrative that takes the PC's involvement into account would do?
So let us say that there is a conflict between two NPCs that the PCs can only watch, have a vital interest in but cannot engage with because (just as one plausible example) they must not be detected at all costs (they are hiding somewhere to find out about this conflict). The conflict is resolved not through force but negotiation. I imagine you playstyle to go through with this as follows: a) you have a table that you roll on who wins the argument. Or b) you use an existing mechanism (just as one possible example: Diplomacy vs. Diplomacy, the higher result wins). The result does not matter to you, so you roll and narrate the result accordingly. Is my understanding correct?
If so: why not just pick a result from the table in a) or pick a winner in your head in b)? What is the added value? All I am seeing is more preptime with a) (and maybe b) because you would probably have to stat out the NPC) and more dice rolling a) and b).