Could it be that a lot of BBC drama's are now made by outside production companies these days? If that is the case the companies might be running on a budget, and the bright young things that produce the shows may have a generic idea of how a certain type of drama should look. So, all Police shows have a similar look/feel, the same as shows like Waking the dead/ Silent witness which are factually incorrect in parts have the same defects. Just a thought.