Yes, there are many factors, unfortunately. "Being in a box" can't explain as much as I'd like. Many drivers seem to freak out if you touch their vehicles, even if there's no damage. They clearly don't want their cars damaged either.

Another major possibility is that they don't think they are driving dangerously at all. Having talked to many drivers over the years, I'm amazed by what people have claimed is perfectly safe to me. (The worst was the guy who passed me too close on an uphill part of the road. I honked at him and he stopped to talk to me. You couldn't see beyond the top of the hill and he was splitting the lanes. Yet he claimed this was perfectly safe.)