but I don't see why one couldn't study aesthetics as 'subjective' (whatever precisely that means), or metaphysics as a skeptic. (In fact, many do each of those things. Just not most.) I guess I can see how devoting your whole life's work to destroying illusions could be a downer, though.

Subjective aesthetics is probably more the realm of psychology (unless it is so subjective that you can't study it). But I'm obviously not saying only Platonists would want to study metaphysics. I'm just saying that the selection effect is sufficient to explain the differences in positions between specialists and non-specialists.