I don't think you understand what a showrunner is. The showrunner is in charge of the stop-and-go decisions, the details, spending the budget allocated by the

I don't think you understand what a showrunner is. The showrunner is in charge of the stop-and-go decisions, the details, spending the budget allocated by the studio. They hire the key crewmembers (DOP, lead writer if not the showrunner, casting director, etc. who then build out the cast and crew. They are as in charge of production as they choose to be: some showrunners micromanage, while others let their crew have a relatively free hand to do their jobs. Of course the studio (usually) has final approval; they're paying for the show. But that doesn't mean the showrunner isn't the boss. It just means that...like every CEO...they still answer to the person with the piggy bank. Also, showrunners aren't as common as you seem to think they are. You might be mixing up showrunners with producers? Producers are as common as weeds. Frequently, writers and cast members are given producing responsibilities and credits for an episode or two, as are many investors, and generally anyone who handles a task that is in any way related to production and has the leverage to demand some sort of credit.