DARK DATA --- Structured / Unstructured {CONFUSION}

According to SPLUNK - "Dark data is all the unknown and untapped data across your organization, generated by systems, devices and interactions. Dark data can be any kind of data. It can be a log file from a website, server, network or application."

 

So all dark data is unstructured data, but not all unstructured data is dark data.

WHY ??? So ... arent Website Logs Structured DATA ??