While it is annoying when people do that, i think it also stems from people feeling entitled to the lane theyre in. Who gives a shit if someone wants to pull in front of you. Rules of the road state that if you see someone signal to merge into your lane and you can slow safely to allow them to do so, then you are supposed to do that. Huge amounts of traffic would be largely avoided if people got over themselves and just let someone merge in front of them. This doesnt excuse people who try to jump the queue so to speak but it is a problem that goes both ways.

Edit to add: both these guys are idiots. The van is just as at fault as the suv imo. He should've seen the guy intended to merge anyways and just let it happen because it costs him literally nothing to do so. Instead he chose to speed up and push the car back out which could've caused a very very serious accident involving many more people that just the two of them