My guess is "leaving the scene" probably doesn't apply here. I drove by a car that ran off the side of the Saw Mill Parkway near NYC at probably 65 mph. By the time, my brain registered what I saw and I could slow down and pull to the side of the road, I was easily at least a mile sounds like the driver came upon the situation post-crash and probably drove by at 60 mph. (Pulling speed out of a hat.)
Driving at normal highway speed could make it really hard to see whether it was a ditch or creek or gully or what-have-you as well.
You certainly are correct.
And the real facts of life are that on most of the interstates, you have to go several miles to an exit, then go back the way you came to the next exit past the accident and by the time you do that you will be at the back end of a traffic jam so long you are of no use anyway.
Most medians on the modern I-s are really wide with trees or banks between lanes or they have crash barries of some sort. Some even concrete walls, as you well know.
It is just that some forget that when they are at their 'puter.