Parkinson has done the rounds and was perceived as a manager on the way down, dropping into non league.
I don't know why Challinor hasn't had a crack at a bigger club, he's never been unsuccessful and is a serial winner. I think part of it is that club owners and chief execs aren't always as clued up on managers, coaches, win stats and under what circumstances as they should be. That's why Mark Hughes keeps getting jobs.