If you want to turn someone into a complete asshole, just put them on wheels. Look no further than the chariot race in Ben Hur for the perfect example of what I mean.
The flow is insidiously intoxicating. You don't have to be a very aggressive person to get addicted to your own smooth progress through space on the flying carpet of your well-suspended automobile. You and I develop a sense of entitlement. I'm driving, here! Step aside! I am the captain of this ship.My decisions are unquestionably correct.
Plenty of wheelers have more of a fighter pilot mentality. And not all rollers exhibit sociopathic tendencies. But sociopathic is not too strong a word for the unconscious but pure self interest that so easily takes over a driver's mind.
It may seem like the opposite of self interest when a driver sets aside safety and traffic law to magnanimously wave another driver into traffic from a driveway or side street, but it shows how sovereign each driver feels to be able to grant this boon. In some traffic-choked locales it is necessary, but frequently it is just a bad idea that balls up the orderly flow.
As someone who frequently gets around on foot or by pedaling a bike I can tell you that no motorist questions that the motor vehicle and its driver belong at the top of the chain of command. I fall into the trap myself, especially during the season when I have to drive a lot. I want to get where I'm going at the speed I choose without a lot of crap from anyone in front or behind me. If I did not have a lot of experience being smaller, slower and more vulnerable I could easily drive in my own little selfish bubble until some impact jolted me out of it.