This is a follow up to my previous question. In general for a system with a given action, from Noether's theorem we have conserved currents for corresponding infinitesimal transformations leaving the action invariant. However $R$-charge as defined in the linked post doesn't generate symmetry transformations on fields constituting the action, but rather acts on the conserved charges.
My problem is, given the fact that $R-$charges don't act on the fields in the Lagrangian itself, what is the utility of introducing them in the first place? Do they serve any convenience upon quantization of the field theory, as classically they don't seem to serve much?