Why doesn't fast-scan cyclic voltammetry work with metal electrodes? Every paper I've seen discussing it uses it with carbon nanofiber or some other carbon material like a diamond. If the physical principles by which it works are based on sweeping through voltages, I don't understand why it can't be used with metal electrodes.

I've tried to search through the literature but I haven't come across any clear answers.
It actually does work. Carbon fiber electrodes are just more useful for the neuro work that fast scans are popular for these days. 

Here is an example from the literature of a metal electrode used up to $3*10^6$ V/s , Amatore et. al. JEAC