Saw an accident happen once in the early 2000s on that stretch of highway southbound (long, boring, some turns, low rolling hills - generally bad for keeping one's attention, but still requiring it). It was a Jeep (Wrangler-style - very short wheel base, very high center of gravity) towing a small PUP (well within limits) without sway control or trailer brakes.
The driver just wasn't paying enough attention when changing lanes and cut off a car with his trailer. The car moved over onto the berm (and probably honked, but I don't really know). The Jeep driver noticed, and jerked back the other direction, but too fast. He braked hard. The (now, badly swaying) trailer pushed him over to the other side of the road until it went off the edge, skewed sideways, and pulled the Jeep off too. The trailer flipped completely over, ending up upside down on the frame with the trailer body detached and left behind. The Jeep ended up on its side.
I think additional training and testing and licensing should be required before towing. Training might not have prevented the initial mistake or the lack of sway control, but there's a good chance the driver would then have reacted better - been more aware of his vehicle's short wheelbase and high center of gravity and the potential impacts of that, eased back the other direction rather than trying to move back too quickly, and countered the sway by speeding up rather than slowing down - that one in particular is VERY non-intuitive in a situation like that.