The GFCI function of an outlet is not intended to protect anyone touching
the outlet plate or screws. It is to prevent whatever is plugged into the
outlet from from becoming a hazard due to leakage or shorts. Since nothing
can be plugged into a switch there is no need for GFCI protection. There are
location and grounding requirements adequate to prevent hazards from
switches.


That makes a lot of sense. Specifically, why switches aren't marketed
with GFCI.
I was suspecting that. Now, I don't think anyone will reach out of the
shower with heavily
dripping hands to turn on the fan, but it occurs to me that you'd
really have to have a switch
heavily saturated with water to make it dangerous. Not so with an
outlet, since the hot
contacts are just a fraction of an inch behind the plate, and a wet
hand could moisten a plug
just enough to make continuity with the prongs.