Well, that doesn’t always work as well as one would hope. And you can also transfer blendshapes to that extent with a few simple tricks using wrap deformers
More range of shapes with less work. There’s only about 25 shapes sculpted for that character.
More freedom for the animators - they’re not bound to sliders, and can push shapes ‘further’ if needed. Also the animators could move the controllers non-linear way between the shapes if they desired.
You really don’t think there’s any merit in this at all?
I think it’s great for cartoon characters - where the shape of the face is more simple because of the stylization and the animators are both expected and also free to push it far.
For a realistic face, precise control, consistency and subtlety are more important. I’m also trying to be more of a modeler than a rigger, maybe that’s another factor.
Also, non-linearity isn’t such an important factor here. Very few people would notice the linear transition with a jaw opening blendshape, but you can recreate the effect of skin and flesh sliding over the jaw bone far better this way. The thing is that every vertex can be moved along a completely different and unique direction, whereas with skinning you’re limited to a single transformation per joint, and so you’ll end up needing a LOT of joints and a lot of tweaking for even just relatively simple actions.
A proper jaw opening motion is almost impossible to do with simple skinning and a single jaw joint, and once you have to add a blendshape to correct the result, you’re ending up with more work to do - weight painting and shape sculpting instead of just the sculpting part.
It’s no wonder that nearly every realistic CG character is built with blendshapes - just as nearly every stylized cartoonish one is using joints.