Have you ever actually observed a truck on the highway? Just drive behind one for about 10 minutes. If you played a drinking game over how many times it fouls the other lane, you'd be DUI before the time is up.
1. Trucks are wider so they have less margin on each side of the lane.
2. When taking a curve, if they are on the outside lane, they are guaranteed to foul the inside lane, simply because a straight line is the shortest path between two points.
3. If the trailer is empty, the wind will cause it to sway erratically.
Also count how many truck tire blowouts you see. That has to cause at least a small loss of control, woe is he that is next to the truck when that happens.
Plus the kinetic energy. Just two days ago: somehow I think the bus would have fared better if it was a mini cooper that crossed the divider... bus-and-fedex-truck-collide-on-i5-bus-in-flames.
Basically, anyone driving adjacent to a truck for more than the 10 seconds it takes to pass one is applying for a darwin award.