GlassJaw
Hero
It's primarily that any monster that is at all specialized in it can grab and hold any PC, unless that PC is a dedicated grappler themselves...which is pretty rare IME. So, it's easy PC-boning.
Granted, you can and should count on your fellow PCs to have words with the monster and eventually get you loose, but if you're, say, a caster or a 2h fighter type, there's little, if anything, for you to do while you're grabbed.
But how does that differ from a fighter with a low Will save failing against a hideous laughter spell? Or confusion? Or any number of save or suck effects? At least with grapple you have a fighting chance?
Trust me, I totally understand the issue. I just see these things as a bigger issue rather than grapple specifically.