There's a huge part of it that is because there's no communication mechanism to resolve conflict on the road, really.
If you're stuck behind someone going slower than you want to, how can you clearly communicate that?
Even in a world where you could clearly speak to them, there's huge potential for disagreement there, and since the only communication mechanisms can very easily be construed as needlessly dangerous or aggressive, of course you're gonna see frustration and anger as a result
“Shocked, disgusted and outraged,” Bechiom alleges that she first ran out of the restaurant but then went back inside to retrieve her guacamole bowl – only to find that her manager and the other co-worker involved in the sexual encounter were vomiting.
Right in front of my salad???