The most likely reason is Mr Sowell does not want a government position. He is an educator and pundit. Why would he want to be a goverment official with the most frustrating job imaginable?
Sowell is trying to influence his students and the public. He is quite effective. Why would he want to run some branch of goverment for a few years. An educator and communicator is not necessarily an administrator.
Miss Condi Rice is one who is a great mind, but I am not sure she is suited as an administrator, . . . or a negotiator. I wonder if she is not actually a good case illustrating your well-accepted point.
Still, GO MR. SOWELL !
I would vote him into office if given the chance, and I'm sure so would most Freepers.