Sometimes sitting on a BF proc until your next GS or sitting on GS until you get a BF proc feels restrictive.
I played IV randomly in a heroic or low M+ a couple weeks ago. It just "felt" better. I love the big GS damage, but I dislike everything else that comes with it.
I get it, those huge GS hits just really fits with that whole 'glass cannon' class fantasy. I don't think I would be playing Frost if GS wasn't there.