Why can’t delete really just delete?

delete keyThanks to television shows like CSI, NCIS and Criminal Minds most people are aware that when you delete something from your computer it isn’t really deleted.

My noobie explanation has always been this. Imagine a textbook with an index in the back. If you decide you want to remove a page, rather than rip the page out of the textbook, you instead go to the index and find the entry in the index pointing to the page you want to remove and you black it out with a Sharpie.

Now anyone looking at the index can’t find your “deleted” page. But someone smart enough to scan the textbook front to back will most certainly still find the page you thought you deleted.

Why do we have to do all of the work?

Savvy techies use software add-ons to make sure a file is really deleted from their computer by writing over the original file with meaningless data (usually ones and zeros) several times. In my textbook analogy, this would be like ripping the actual page out of the book and burning it.

So my question is this. Why do we have to jump through hoops to truly delete a file? Why can’t operating systems like Windows 7 do all the cool techie stuff to permanently destroy a file for me?

In other words, why can’t delete really just delete?