Moving these control points allows you to reshape the model smoothly.
If you are looking to create unique, soft-edged, or warped designs, taking the time to learn Sketchy FFD is a move you won't regret. If you want, I can:
Designing ergonomic products—like the curve of a mouse, the bend of a plastic chair, or the hood of a car—requires smooth transitions. Sketchy FFD makes it easy to create those "blob-like" forms that are difficult to achieve with the standard Scale or Rotate tools.