That's because they cycle the same coaches around. Retread, same ole, same ole. It's all politics.
It's not all politics. It's just a pain in the arse to hire people.
First off, whatever school is hiring someone has to have a teaching job available in that coach's certification area.
Then, each coach has to go through job fair. Lets take Lakeshore for instance. Larry Route stepped down right after the season. If Lakeshore wanted to hire someone from outside of St. Tammany Parish, the new coach would have to go through job fair in June. So you're looking at a new head coach coming in 2 months before the season begins. Then, good luck hiring assistants.
It's a complete pain in the ass.