But they're NOT fun, that's what you're not getting here. They're fetch quests full of nonsense and bulltrout. There's literally no way to know certain monster spawn conditions or where certain items are located, without a guide. There's literally no way to know if the answer is Heads or Tails.
So if the sidequests aren't fun, and have no real impact on the story, why should they be mandatory for learning a rather huge fact like Caius is still alive?