Dark data is all the information businesses collect but never use—like old...

https://technivorz.com/why-does-dark-data-matter-for-ai-projects/

Dark data is all the information businesses collect but never use—like old emails or files gathering dust. It makes up about 60-80% of stored data and can hide risks or costs. Ignoring it wastes roughly $2.5 million per year in storage and management fees