I have been given a different understanding of these "grab my wrist" scenarios. (this is what I have been told... if someone knows different, let me know...) I have been told that this is from the time when people wore their sword on their left side. The sword could not be drawn by the left hand, so you wanted to keep the right hand controlled and away from the sword. If it got to the sword, and he drew the sword, things got very bad for you. Also, it was not simply a wrist grab, but a wrist grab and take down, to the rear. The idea was for the unarmed guy to surprise the swordsman, grab his wrist, preventing the sword draw and taking him down.
So the wrist grab escape, was really about freeing your hand, to get to your sword. Even the "circle the guys grabbing hand, and wrist lock him" escape works for getting to the sword. Forget the lock, circle around his grabbing hand, and draw your sword, cutting him in the draw.
This is what I have been taught, and I would be interested on thoughts about how authentic that is. However, it does give a reason for the grab. You can then move the techniques out of the static realm, by having the attacker grab your wrist and attempt to take you down to the rear. You have to regain your structure and do the escape, as the attacker is trying to take you down, or at least off balance.
These days people don't wear swords, so this attack is less real. But, someone may grab you that way to prevent you from grabbing a weapon of opportunity, or possibly to force you into a car, or out a door... The practice of moving with, to regain your balance and escape, now that a real intent has been added to the "grab my wrist" attack, helps you to learn the underlying principals and body mechanics. Those principals and mechanics can be useful in many other situations, that are more probable.