Poor Work From Detective Writers.

Why is it in detective stories, either in books or on the screen, there are so very few Detective Constables?
There's usually a an array which consists of:
One Superintendent.
At least one DCI.
Typically, two Detective Inspectors.
One Detective Sergeant and
A maximum of 2 DCs.

What is matter with all these authors - and they are many?
A classic case of 'too many chiefs and not enough indians'. (With apologies to any Native American readers.)