Why is the NFL so insistent on retreads and failed coaches getting another chance?

-There are 8 head coach openings in the NFL, and some names that are popping up for jobs are guys who have been fired recently (Adam Gase, Mike Munchak…..and yes, somehow, Kliff Kingsbury)

-Gase and Munchak are maybe understandable (did make playoffs once in their tenures)…but why is a guy like Vance Joseph (who went 11-21 in 2 seasons in Denver) getting an interview from the Bengals?