It's been my theory that there are so many wrists grabs taught in systems like Aikijujutsu and other japanese systems because of the holdover from the samurai period, when attacking the weapon hand to control it, to prevent the drawing of the sword, was common. In that sense, wrist grab training is a bit anachronistic. It's much like the old story about the little girl and the ham.
"A little girl asks her mother, who's preparing for Thanksgiving dinner 'mom, why do you cut the ends off of the ham before putting it in the oven'? Mom responds, 'I don't know, your grandmother always did it that way, so I do to'. So the little girl asks her grandmother the same question. The grandmother responds, 'well, it's the way your great grand mother always did it, so I did it that way, go ask your great grand mother.' So the little girl asks her great grand mother about cutting the ends off of the ham. Great grand mother laughs and says 'well, I don't know why your mother and grand mother do it, but I always did it because my pan was too small to fit the ham in.'"
Not to say that teaching a couple of wrists grabs is a bad idea, but imho spending a lot of valuable training time training wrists grabs is a disservice to those who are expected to use the techniques taught them to defend themselves.