True. English isn't my native language and I thought about this, but it somehow just makes sense in my head. The way the "just" is used reminds me of the Modalpartikel we have in German. They're basically filler words that add nuance, emphasis or expectation to a sentence.

Sometimes people ask "Just why?", and that's a bit different than only "Why?", because it adds a sense of confusion or urgency to the question.