You'd be surprised how few people don't follow the "rules" of etiquette, even at the highest levels of racing. Many people have it in their head that they are better than their finishing times indicate, so they refuse to pull aside unless the announcer calls it.

There are other times, though, where one guy yells "hack" when the other guy just made a mistake. Not everybody who overshoots a corner intended to take out the guy in front of him. In fact, I'd say that in most cases, this is probably what happens; so before you start yelling at somebody for hacking, make sure they really deserve it.