Because their performance matrices are evaluated by how closely they follow their SOP. They are forced to follow it even if it’s brain dead. It is up to the ones setting the policies and procedures (the management) to make sure that their SOP and workflow they put in actually works.
If the management don’t give a shit, keep giving bullshit orders and setting bullshit targets, workers with common sense will leave from all the frustration, leaving only the kinds of people you met running the department.