Of course, nobody is doing big-wall climbing with a grigri

What are you talking about? Pretty much everyone on big walls is carrying a gri. In addition to giving lead belays, they are more pleasant to use for top down belays, and can be useful for hauling, juggin, lowering out, rappelling, or any number of other big wall chores. Yes, they are relatively heavy, but so is the number six you are lugging up the face so you can place it once on the scary offwidth pitch.