In Taekwondo we normally divide up Our training into the 5 pillars of Taekwondo; Basics, Forms, Sparring, Self defense and Breaking (or Gibon Dongjak, Poomsae, Kyorugi, Ho Sin Sul and Kyopka respectivly).
In the self defense part of Taekwondo the focus is normally on freeing yourself from various grips. At least that is how I often see it practised and taught. Personally I think that Ho Sin Sul is Applied Taekwondo as a Whole, and freeing Your self from various grabs is just one part of it all, but it is a very important skill nonetheless and especially so for Taekwondoin who focus on striking. Having an arm grabbed, or someone does a bear hug over Your arms for instance means that the opponent has tied up one (or more) of Your striking Tools. If you base Your self defense on striking the opponent to remain safe from harm, having Your striking Tools removed is not good... Therefore I do see why this becomes the main focus for many Peoples Ho Sin Sul training.
A thing that is a little facinating though is the seemingly Obsession With wrist grabs that You will find not only in Taekwondo and its sister art Karate but in almost every Martial Art of the East... It has gotten to the point that for some the releasing and countering to wristgrabs account for the majority of their Ho Sin Sul training and that cant be good, can it?