Because I love making generalizations based on personal experience: most of the bad drivers I encounter on the road are either pickup trucks, BMWs, or rusted out junkers.
The trucks have no regard for others' safety, because they know if they get in an accident they will squash a smaller vehicle. They take this to the point of just swerving into your lane, counting on you to break or get out of the way.
BMWs are simply unskilled, unpredictable, selfish drivers. They are too self-obsessed to cater their driving to anyone else on the road. They will take up lanes they don't need to be in and do illegal maneuvers to correct their mistakes, because they believe they are above the law.
The junkers are just batshit methheads or something. They have no regard for anyone's safety, including their own. They have a drug deal they are trying to get to.