After decades of hearing that "delete" does not really make the data impossible to recover, I have to ask WHY the OS was not corrected long ago to do what it should have been doing all along? What is the big deal? Can't the system just trundle along in the background over-overwriting and whatever else has to happen? Why do we need additional utilities to do what we always thought was happening? What is the motivation of OS developers to NOT correct this problem?

ADDITION: This is not a technology question, because clearly it IS possible to delete things securely, or else there would not be tools available to do it. It is a policy question: If some people feel that it is important and should be part of the OS, why is it not part of the OS? Many things have been added to OSes over the years, and this could certainly be one of them. And it IS an important issue, or there would not have been articles and stories about it for about 3 decades now. What is with the inertia? Just do the right thing.

Because of the following reasons:


Performance - it takes up resources destroying files. Imagine an application that uses hundreds or thousands of files. It would be a huge operation to securely delete each one.
Extra wear and tear on the drives.
Sometimes the ability to retrieve a file is a feature of the OS (e.g. Trash, Recycle Bin, Volume Shadow Copy).
As noted by Xander, sometimes the physical storage mechanism is abstracted from the OS (e.g. SSDs or network drives).

