When doing that it is not seldom that I trigger or complete a quest not yet given to me. It could be by killing a sorcerer in a cave, or finding a special item. Bad games never put interesting things or places beyond the main roads like Arcania - Gothic 4. A big world but totally without content beyond the quests given.
So far so good but here is where RPGs traditionally differs. The good ones let you get into the quest by informing you that the quest is completed, perhaps by showing it´s name or giving you xp. Then you know you´ve done something good and gets some credit for it. If the game also let´s you complete the quest when you later see the quest giver, all the better because then you get the reward for the quest as well.
But these are the good games. With a system like that you take no risks or chances by this playing style other than that it could have been nice to know the context of the quest before you completed it. But that´s ok.
Now, the bad games will just remove the quest from the game without informing you when you complete it and you will never be given it in the first place. You will miss out on both XP and a potential reward for the quest. Such games spoiles the fun of exploration and forces you to stay to the main quest and roads in order not to trigger them until you´ve been given them.
Unfortunately I cannot find any example of these bad games but I know there are several that have crossed my path amongst the classical RPGs of the last decades.
Do you have any exampels of the games that handles this bad ?