It is tricky to get someone to recognise that they aren't knowlegable enough. Even if you say it as gently as possible, some will still hear "you're dumb" and no one likes that.
Also it's a great tool to manipulate people : "I don't need a scientist trying to explain me life from the depths of their lab !! I have commonsense !!"
playing in a symphonic orchestra. sure, it sounds cool, but most people don't know much about the topic and feel intimidated by it, so the conversation is just me attempting to convince them that it's not just for rich nerds and you can be casual about classical music.