Why no CAS turboprops?

A question-- why haven't any CAS aircrarft been designed with
turboprops or the pusher varient (I foreget what you call it)? Given
their slow operating speed, it would seem to be a natural match up. Is
it a case the they are obsolete, or more of a case that people (read--
budget officials) have come to expect *jets*, on military aircraft.
Also, after a brief flurry of interest in USB (Upper surface
blowing) combat aircraft in the 1980's, nothing seems to have come of
it. The predicted STOL and payload advantages were rather
impressive-- did engineering problems come to the fore?