Most people remember the "idea" of Ledger's Joker but forget the actual reality of what he did, and the fact that all his "philosophy" was proven to be actually false by the movie itself. Including when he tried to force it in a huff after it failed to materialize.

But that's not edgy and cool enough, so everyone just jerks off over "chaos lul" the same way they treated the guy from Jurassic Park saying "chaos theory" as super smart.