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.
The niceness is especially dangerous when someone on a four-lane (in town with lots of traffic) stops short to wave someone oncoming to turn left in front of them, when there is another lane of traffic next to them with the right of way that has no intention of stopping or any warning that they will need to. It could be a fatal broadside collision.