SHOWLAYERUSAGE

 There appears to be a setting in AutoCAD that will prevent layers from indicating if objects are on them or not. The system variable is SHOWLAYERUSAGE. A value of 0 turns of the ability of AutoCAD to show if objects are on a layer. A value of 1 enables the ability of AutoCAD to indicate if a layer is in use. 

It appears this variable was created to improve drawing performance. In Civil 3D the value defaults to 0, or OFF. So if you want to see layer usage then you will want to set the value to 1. Not sure how badly this affects drawing performance. It sure would be nice if Autodesk created another thread to do the work instead of having it on the UI thread that makes the drawing performance go down. 

I guess if you hear an Autodesk developer say they can't think of a reason why multithreading is necessary, you can point them to this workaround they did instead of utilizing multithreading.