Being toxic on your own server rarely has repercussions - particularly if you’re already in a guild and have secured your raid spot.
Over half of the worst instances of dungeon toxicity I ever saw were before RDF and came from someone with at least two other members of their guild present. IE: they were being terrible right in front of - and thus effectively with the support of - their guild. Why would they care what a couple of randos thought about what happened in a dungeon? They were there for badges or to help gear up a member of their guild and everyone else could go jump off a cliff.
Just this week I has sitting on top of a nightmare vine killing the mob that aggroed when someone flew down and snaked it out from under my butt - literally. I recognized him as the main tank of a really active guild. Do you honestly think anyone in his guild is going to care about him pulling a Richard move?
RDF makes sure that we don’t have to rely on people like that for gear.