"Derrida and Badiou at Tanagra!"
It's like this because like the Tamarians, everyone in the discussion is assumed to be familiar with all of the background material -- and if you are not, then what the hell are you doing here? I saw this kind of elitism unfold here on Hackernews once. Someone once asked for an explanation of what deconstruction was and was told basically, "Have you read your Husserl, Heidegger, Hegel, Nietzche, Freud, and Levinas yet? No? Then shaddap, you are obviously not prepared to even begin to understand deconstruction." Can you imagine Feynman doing that? Like, "Have you read your Newton, Leibniz, Maxwell, Einstein, Bohr, and Schrödinger yet? No? Then shaddap..."
Philosophy is like AI: as soon as we know it works and put it into practice, it ceases to be philosophy. So people who majored in philosophy are put in the uncomfortable position of having to justify the importance -- to others and perhaps themselves -- of what they study, and it's much easier to seem important by forming exclusive intellectual cliques and inventing ways to consider people outside your clique to be stupid and wrong-headed than it is to dig deep and find out why and how your work is important in the real world -- or, worse yet, face the music and admit your work is not important at all and you're better off doing something else.