It is the normal routine, they have more important places to be.
It is not as bad if it is between the front car and the load, that is something that will happen.
The lead car is out there to give the load notice of shoulder activity, lane blockages, etc.
so that the rear car and the load can move to avoid the hazard in a safe and timely fashion.
Invariably that will happen, not supposed to but it does.
The type of load has a great deal to do with what is required. If the load is just long or extremely wide letting the driver know there is a car right there, and leaving them enough room to get out from behind the load is usually all it takes to prevent any serious problems.
On the bad side if there is an overhang (especially one that is flexible, up and down) then you can only attempt to make the vehicle that got between you and the load aware of the peril.
If the escort is positioned properly, that should be enough of a deterrent to keep them from running up under the load.
I have been on the other end driving the big load for over three decades, communication between both truck and escort vehicle is paramount. Awareness of surroundings and ability for both parties to work well together keeps a lot of unpleasant situations from developing in the first place.