I look at it this way: those teams are in a similar position to USF in that they can't pull the five star candidates they'd like for the reasons you mention (and others). So they end up taking people with question marks (Petrino, Tuberville, Nutt, Freeze, Kiffin) and hope they work out.
In the same way the Clemson assistants look to have turned down USF, many smart coaches (the ones without Kiffin's baggage) would rather hold out for a better situation if their resume warrants it.