if nothing is his job, why do clubs employ head coaches?
You’re the one who keeps saying nothing is his job.
The head coach is responsible for plenty of stuff. What he isn’t responsible for is recruitment/retention and pathways. Also cap management, negotiating TPAs for players, the reserve grade side, building/renting facilities, taking home games interstate or organising transport to games.
Let’s just say there’s plenty of stuff that’s not his job, but he stays busy enough coaching the NRL side. It’s literally a full time job, even with all the assistant coaches and other staff.