I’m a transplant to the rural Georgia. And here, it isn’t passive-aggression. It’s seen as someone being nice and neighborly.
It makes me nervous and frustrated, because I’m afraid that I will become the victim in an accident. I can just hear the kind, neighborly lady trying to explain to the sheriff’s deputy, “I was just trying to be polite. I don’t know why she is so upset that the other driver crossed in front of her and hit her car!”
It’s seen as someone being nice and neighborly.
Same here in SD. but as you note, still a very dangerous practice, and the one practicing it will more than likely not be the one that has the accident, that their misguided niceness caused. It is why there is a drivers manual with the rules of the road, in each state.