Let's say we're living in the Matrix or Plato's cave. And thus you're being tricked and don't know the truth about reality.
Now, let's say you don't know this, but you have some intuition that this might be the case. Why does it matter? Would it change how you live, how happy you are? Note I am not just talking about truth in the metaphysical sense, but also in things like knowing the truth regarding certain things that did/n't happen: did your ex lie to you? Does this person really like you back?
Is knowing the truth good in itself or is it a practical question of having the information you need at hand? Or does it not matter?