Because the files are not actually deleted. You are simply wrong! The fact is - when you empty the Recycle Bin, or using other similar methods (such as Command + Shift + Del) to remove unnecessary files you though that prevented the trash, then almost certainly still recoverable. Sulution 1: Thought Empty Trash to Delete Files Permanently? NO!
Looking for a solution of this type that can be used to protect remove the Macintosh hard drive before reselling your old Mac machine, so have to worry about people (mostly computer geeks) has any chance of data recovery from the old computer! It gets to the right place and focus on the need to clean Mac and how doing the work in selective options, based on the particular circumstances.