Customize This View - choices all grayed out

I’ve never used this before. A user called me to say that some of the views in the application will not allow customization via “Customize This View”. The options are all grayed out. I can’t seem to find a rhyme or reason for this. Can anyone tell me why the “Customize This View” may not be available?

Subject: Customize This View - choices all grayed out

The developer did not check the “Allow customizations” option for the view. It is on the second tab of the View Properties box.