There are games that do this, and frankly I think it's an important step. Sometimes not even requiring the NPC to see it so much as flagging a task completion on the player to potentially open a new dialog with the NPC. E.g. - player kills 100 wolves while picking alchemy reagents. Player runs into farmer and initiates dialog where farmer offers quest for killing 5 wolves. The flag allows the player to say "oh, I've already killed dozens of wolves today" and the farmer is happy, pays up, and the quest is complete. This could be expanded, possibly (with some added complication) where the player could lie about completing quests where no evidence is required. This could lead to all sorts of fun ramifications. This would also play well in an RPG where alignment mattered.